diff --git a/.github/workflows/golangci-lint.yml b/.github/workflows/golangci-lint.yml
index ef3d3bffd..e5d2fedda 100644
--- a/.github/workflows/golangci-lint.yml
+++ b/.github/workflows/golangci-lint.yml
@@ -16,7 +16,7 @@ jobs:
       # Config options can be found in README here: https://github.com/golangci/golangci-lint-action
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
       - uses: actions/checkout@v3
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v3
diff --git a/.github/workflows/govulncheck.yml b/.github/workflows/govulncheck.yml
index 538c436bc..62a3ca54e 100644
--- a/.github/workflows/govulncheck.yml
+++ b/.github/workflows/govulncheck.yml
@@ -14,6 +14,6 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
       - run: go install golang.org/x/vuln/cmd/govulncheck@latest
       - run: govulncheck -show=stacks -test ./...
diff --git a/.github/workflows/nightly-tests.yml b/.github/workflows/nightly-tests.yml
index f579f1b65..6dc3a1968 100644
--- a/.github/workflows/nightly-tests.yml
+++ b/.github/workflows/nightly-tests.yml
@@ -11,7 +11,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
       - uses: actions/cache@v3
         with:
           path: |
diff --git a/.github/workflows/pre-commit.yml b/.github/workflows/pre-commit.yml
index 29ddb16aa..5d668e670 100644
--- a/.github/workflows/pre-commit.yml
+++ b/.github/workflows/pre-commit.yml
@@ -16,7 +16,7 @@ jobs:
       - uses: actions/setup-python@v2
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
       - uses: pre-commit/action@v2.0.3
 
       - name: notify failure
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 2625013fc..3ade57421 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -15,7 +15,7 @@ jobs:
         fetch-depth: 0 # Disable shallow checkout
     - uses: actions/setup-go@v4
       with:
-        go-version: '1.21.3'
+        go-version: '1.21.4'
     - run: go run . --help > cli-reference.txt
     - run: go run testutil/genchangelog/main.go
     - uses: softprops/action-gh-release@v1
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 807fcb602..9dfe5191e 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -11,7 +11,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
       - uses: actions/cache@v3
         with:
           path: |
@@ -33,7 +33,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
       - uses: actions/cache@v3
         with:
           path: |
@@ -51,7 +51,7 @@ jobs:
       - uses: docker/setup-buildx-action@v2 # For compose to build images
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
       - uses: actions/cache@v3
         with:
           path: |
@@ -78,7 +78,7 @@ jobs:
       - uses: docker/setup-buildx-action@v2 # For compose to build images
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
       - uses: actions/cache@v3
         with:
           path: |
diff --git a/.github/workflows/verify-pr.yml b/.github/workflows/verify-pr.yml
index d1a317541..bf5d1c775 100644
--- a/.github/workflows/verify-pr.yml
+++ b/.github/workflows/verify-pr.yml
@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.3'
+          go-version: '1.21.4'
 
       - name: "Verify PR"
         run: go run github.com/obolnetwork/charon/testutil/verifypr
diff --git a/.golangci.yml b/.golangci.yml
index 0829aabc7..579ab883c 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -1,6 +1,6 @@
 run:
   timeout: 5m
-  go: "1.21.3"
+  go: "1.21.4"
 linters-settings:
   cyclop:
     max-complexity: 15
@@ -99,7 +99,7 @@ linters-settings:
          - "github.com/gogo/protobuf/proto" # Prefer google.golang.org/protobuf
          - "github.com/prometheus/client_golang/prometheus/promauto" # Prefer ./app/promauto
   staticcheck:
-    go: "1.21.3"
+    go: "1.21.4"
     checks:
      - "all"
      - "-SA1019" # Ignoring since github.com/drand/kyber/sign/bls uses Proof Of Possession as does Ethereum.
diff --git a/Dockerfile b/Dockerfile
index 80e7c5f69..b9f3a6b84 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 # Container for building Go binary.
-FROM golang:1.21.3-bullseye AS builder
+FROM golang:1.21.4-bullseye AS builder
 # Install dependencies
 RUN apt-get update && apt-get install -y build-essential git
 # Prep and copy source
diff --git a/app/eth2wrap/synthproposer.go b/app/eth2wrap/synthproposer.go
index 184b270c8..b049d5520 100644
--- a/app/eth2wrap/synthproposer.go
+++ b/app/eth2wrap/synthproposer.go
@@ -7,6 +7,7 @@ import (
 	"crypto/sha256"
 	"encoding/binary"
 	"fmt"
+	"net/http"
 	"sync"
 
 	eth2client "github.com/attestantio/go-eth2-client"
@@ -141,16 +142,20 @@ func (h *synthWrapper) BlindedProposal(ctx context.Context, opts *eth2api.Blinde
 func (h *synthWrapper) syntheticProposal(ctx context.Context, slot eth2p0.Slot, vIdx eth2p0.ValidatorIndex) (*eth2api.VersionedProposal, error) {
 	var signedBlock *eth2spec.VersionedSignedBeaconBlock
 
-	// Work our way back from previous slot to find a proposal to base the synthetic proposal on.
+	// Work our way back from previous slot to find a block to base the synthetic proposal on.
 	for prev := slot - 1; prev > 0; prev-- {
 		opts := &eth2api.SignedBeaconBlockOpts{
 			Block: fmt.Sprint(prev),
 		}
 		signed, err := h.Client.SignedBeaconBlock(ctx, opts)
 		if err != nil {
+			if apiErr := new(eth2api.Error); errors.As(err, apiErr) { // Continue if block is not found in the given slot.
+				if apiErr.StatusCode == http.StatusNotFound {
+					continue
+				}
+			}
+
 			return nil, err
-		} else if signed == nil { // go-eth2-client returns nil if proposal is not found.
-			continue
 		}
 
 		signedBlock = signed.Data
diff --git a/app/obolapi/api.go b/app/obolapi/api.go
index 02ef3d18e..95767c354 100644
--- a/app/obolapi/api.go
+++ b/app/obolapi/api.go
@@ -49,9 +49,10 @@ func (c Client) url() *url.URL {
 	return baseURL
 }
 
-// PublishLock posts the lockfile to obol-api.
+// PublishLock posts the lockfile to obol-api. It has a 30s timeout.
 func (c Client) PublishLock(ctx context.Context, lock cluster.Lock) error {
-	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
+	// TODO(xenowits): Reduce the timeout once the obol-api is optimised for publishing large lock files.
+	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
 	defer cancel()
 
 	addr := c.url()
diff --git a/testutil/compose/static/lighthouse/run.sh b/testutil/compose/static/lighthouse/run.sh
index 46b07fbe0..67a23d686 100755
--- a/testutil/compose/static/lighthouse/run.sh
+++ b/testutil/compose/static/lighthouse/run.sh
@@ -23,5 +23,5 @@ done
 echo "Starting lighthouse validator client for ${NODE}"
 exec lighthouse validator \
   --testnet-dir "/tmp/testnet" \
-  --beacon-node "http://${NODE}:3600" \
+  --beacon-nodes "http://${NODE}:3600" \
   --suggested-fee-recipient "0x0000000000000000000000000000000000000000"
diff --git a/testutil/promrated/Dockerfile b/testutil/promrated/Dockerfile
index de1b49ee2..60fe44f05 100644
--- a/testutil/promrated/Dockerfile
+++ b/testutil/promrated/Dockerfile
@@ -1,4 +1,4 @@
-FROM golang:1.21.3-alpine AS builder
+FROM golang:1.21.4-alpine AS builder
 
 # Install dependencies
 RUN apk add --no-cache build-base git