diff --git a/docs/Installation.ipynb b/docs/Installation.ipynb
index 97c1e0768..ef53063b8 100644
--- a/docs/Installation.ipynb
+++ b/docs/Installation.ipynb
@@ -8,16 +8,19 @@
    },
    "outputs": [],
    "source": [
-    "from markdown import markdown\n",
     "import sys\n",
-    "sys.path.insert(0, '..')\n",
+    "\n",
+    "from markdown import markdown\n",
+    "\n",
     "from versions import (\n",
     "    JUPYTER_LSP_VERSION,\n",
     "    JUPYTERLAB_LSP_VERSION,\n",
     "    JUPYTERLAB_NEXT_MAJOR_VERSION,\n",
     "    JUPYTERLAB_VERSION,\n",
-    "    REQUIRED_JUPYTERLAB\n",
-    ")"
+    "    REQUIRED_JUPYTERLAB,\n",
+    ")\n",
+    "\n",
+    "sys.path.insert(0, \"..\")"
    ]
   },
   {
diff --git a/packages/jupyterlab-lsp/src/adapters/codemirror/features/hover.ts b/packages/jupyterlab-lsp/src/adapters/codemirror/features/hover.ts
index 536056797..05e6324fe 100644
--- a/packages/jupyterlab-lsp/src/adapters/codemirror/features/hover.ts
+++ b/packages/jupyterlab-lsp/src/adapters/codemirror/features/hover.ts
@@ -201,7 +201,7 @@ export class Hover extends CodeMirrorLSPFeature {
           e.message === "Cannot read property 'string' of undefined"
         )
       ) {
-        throw e;
+        console.warn(e);
       }
     }
   };
diff --git a/packages/jupyterlab-lsp/src/command_manager.ts b/packages/jupyterlab-lsp/src/command_manager.ts
index 69e7d11e1..07e41ef03 100644
--- a/packages/jupyterlab-lsp/src/command_manager.ts
+++ b/packages/jupyterlab-lsp/src/command_manager.ts
@@ -201,7 +201,7 @@ export class NotebookCommandManager extends ContextCommandManager {
     return notebook_adapters.get(notebook.id);
   }
 
-  context_from_active_document(): ICommandContext {
+  context_from_active_document(): ICommandContext | null {
     if (!this.is_widget_current) {
       return null;
     }
@@ -213,7 +213,7 @@ export class NotebookCommandManager extends ContextCommandManager {
 
     let virtual_editor = this.current_adapter?.virtual_editor;
 
-    if (!virtual_editor) {
+    if (virtual_editor == null) {
       return null;
     }
 
@@ -222,6 +222,11 @@ export class NotebookCommandManager extends ContextCommandManager {
       cm_cursor
     );
 
+    if (root_position == null) {
+      console.warn('Could not retrieve current context', virtual_editor);
+      return null;
+    }
+
     return this.current_adapter?.get_context(root_position);
   }
 }
diff --git a/packages/jupyterlab-lsp/src/manager.ts b/packages/jupyterlab-lsp/src/manager.ts
index 68028af48..ade479059 100644
--- a/packages/jupyterlab-lsp/src/manager.ts
+++ b/packages/jupyterlab-lsp/src/manager.ts
@@ -53,7 +53,8 @@ export class LanguageServerManager implements ILanguageServerManager {
     );
 
     if (!response.ok) {
-      throw new Error(response.statusText);
+      console.error('Could not fetch sessions', response);
+      return;
     }
 
     let sessions: SCHEMA.Sessions;
diff --git a/packages/jupyterlab-lsp/src/virtual/editors/notebook.ts b/packages/jupyterlab-lsp/src/virtual/editors/notebook.ts
index 00578410c..fdcb00f83 100644
--- a/packages/jupyterlab-lsp/src/virtual/editors/notebook.ts
+++ b/packages/jupyterlab-lsp/src/virtual/editors/notebook.ts
@@ -118,11 +118,12 @@ export class VirtualEditorForNotebook extends VirtualEditor {
   transform_from_notebook_to_root(
     cell: Cell,
     position: IEditorPosition
-  ): IRootPosition {
+  ): IRootPosition | null {
     // TODO: if cell is not known, refresh
     let shift = this.cell_to_corresponding_source_line.get(cell);
-    if (shift === undefined) {
-      throw Error('Cell not found in cell_line_map');
+    if (shift == null) {
+      console.warn('Cell not found in cell_line_map');
+      return null;
     }
     return {
       ...(position as CodeMirror.Position),
diff --git a/packages/lsp-ws-connection/src/server-capability-registration.ts b/packages/lsp-ws-connection/src/server-capability-registration.ts
index 12d158634..765612cc3 100644
--- a/packages/lsp-ws-connection/src/server-capability-registration.ts
+++ b/packages/lsp-ws-connection/src/server-capability-registration.ts
@@ -11,7 +11,7 @@ interface IFlexibleServerCapabilities extends ServerCapabilities {
 function registerServerCapability(
   serverCapabilities: ServerCapabilities,
   registration: Registration
-): ServerCapabilities {
+): ServerCapabilities | null {
   const serverCapabilitiesCopy = JSON.parse(
     JSON.stringify(serverCapabilities)
   ) as IFlexibleServerCapabilities;
@@ -27,7 +27,8 @@ function registerServerCapability(
       );
     }
   } else {
-    throw new Error('Could not register server capability.');
+    console.warn('Could not register server capability.', registration);
+    return null;
   }
 
   return serverCapabilitiesCopy;
diff --git a/packages/lsp-ws-connection/src/ws-connection.ts b/packages/lsp-ws-connection/src/ws-connection.ts
index 24acea4eb..cd3ff9b99 100644
--- a/packages/lsp-ws-connection/src/ws-connection.ts
+++ b/packages/lsp-ws-connection/src/ws-connection.ts
@@ -79,10 +79,14 @@ export class LspWsConnection extends events.EventEmitter
           (params: protocol.RegistrationParams) => {
             params.registrations.forEach(
               (capabilityRegistration: protocol.Registration) => {
-                this.serverCapabilities = registerServerCapability(
-                  this.serverCapabilities,
-                  capabilityRegistration
-                );
+                try {
+                  this.serverCapabilities = registerServerCapability(
+                    this.serverCapabilities,
+                    capabilityRegistration
+                  );
+                } catch (err) {
+                  console.error(err);
+                }
               }
             );