Assertion `*rt == witnesses[i]->root()' failed (recheck of the sapling notes witness height)

[Sil3ntVip3r]

It seams the wallet gets this error randomly when using Z addresses.
The error below is the error from the node.
Reference attached image for more info.

This could be the solution (recheck of the sapling notes witness height):
https://github.com/zcash/zcash/blob/c791f0a770c832c8f8dd20c62091781a276858e9/src/wallet/wallet.cpp#L3923

Feb 27 15:20:50 bitcoinzd[2062777]: bitcoinzd: wallet/wallet.cpp:1971: void CWallet::GetSaplingNoteWitnesses(std::vector, std::vector<boost::optional<libzcash::IncrementalWitness<32, libzcash::PedersenHash> > >&, uint256&): Assertion `*rt == witnesses[i]->root()' failed

[MarcelusCH]

There is currently no solution to this problem. Only a workaroud, restart the node with rescan option : bitcoinzd -rescan.

This is annoying, especially if a lot of transactions were carried out with this wallet.

[MarkLTZ]

To get root cause of this issue a patched node is needed:

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 1b9e6124f..68a0db8bd 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1981,11 +1981,17 @@ void CWallet::GetSaplingNoteWitnesses(std::vector<SaplingOutPoint> notes,
     LOCK(cs_wallet);
     witnesses.resize(notes.size());
     boost::optional<uint256> rt;
+    boost::optional<int> witnessHeight;
     int i = 0;
     for (SaplingOutPoint note : notes) {
         if (mapWallet.count(note.hash) &&
                 mapWallet[note.hash].mapSaplingNoteData.count(note) &&
                 mapWallet[note.hash].mapSaplingNoteData[note].witnesses.size() > 0) {
+            if (!witnessHeight) {
+                witnessHeight = mapWallet[note.hash].mapSaplingNoteData[note].witnessHeight;
+            } else {
+                assert(*witnessHeight == mapWallet[note.hash].mapSaplingNoteData[note].witnessHeight);
+            }
             witnesses[i] = mapWallet[note.hash].mapSaplingNoteData[note].witnesses.front();
             if (!rt) {
                 rt = witnesses[i]->root();

This code must be added and compiled only on the node where the issue is happening and removed after got all information needed to solve it.

[MarkLTZ]

#99 should fix this issue, but it require on affected wallets a firstrun using options -zapwallettxes=2 -rescan.