I ran bitcoin-qt with an old wallet, causing it to rescan, then stopped it with a SIGINT signal, resulting in the following log. Nothing unexpected, so far:
```
2022-03-05T16:01:03Z init message: Loading wallet…
2022-03-05T16:01:03Z BerkeleyEnvironment::Open: LogDir=…/.bitcoin/database ErrorFile=…/.bitcoin/db.log
2022-03-05T15:57:18Z [walletname.dat] Wallet File Version = 159900
2022-03-05T15:57:18Z [walletname.dat] Keys: 2397 plaintext, 0 encrypted, 2397 w/ metadata, 2397 total. Unknown wallet records: 0
2022-03-05T15:57:18Z [walletname.dat] Wallet completed loading in              65ms
2022-03-05T15:57:18Z init message: Rescanning…
2022-03-05T15:57:18Z [walletname.dat] Rescanning last 134072 blocks (from block 591711)...
2022-03-05T15:57:18Z [walletname.dat] Rescan started from block 000000000000000000075fcc1872da61f45bcfd0e0bb36b7c8cb45e7a328ad41...
2022-03-05T15:58:18Z [walletname.dat] Still rescanning. At block 593552. Progress=0.632716
2022-03-05T15:59:18Z [walletname.dat] Still rescanning. At block 595458. Progress=0.638084
2022-03-05T15:59:37Z [walletname.dat] Rescan interrupted by shutdown request at block 596080. Progress=0.639932
2022-03-05T15:59:37Z Error: Failed to rescan the wallet during initialization
2022-03-05T15:59:41Z GUI: initializeResult : Initialization result:  false
2022-03-05T15:59:41Z GUI: requestShutdown : Requesting shutdown
2022-03-05T15:59:41Z GUI: Running Shutdown in thread
2022-03-05T15:59:41Z Shutdown: In progress...
2022-03-05T15:59:41Z scheduler thread exit
2022-03-05T15:59:42Z Shutdown: done
2022-03-05T15:59:42Z GUI: Shutdown finished
2022-03-05T15:59:42Z GUI: ~InitExecutor : Stopping thread
2022-03-05T15:59:42Z GUI: ~InitExecutor : Stopped thread
```

However, the next time it was launched, the rescan didn't continue, nor did it start over. It seems to have been skipped?
```
2022-03-05T16:01:03Z init message: Loading wallet…
2022-03-05T16:01:03Z BerkeleyEnvironment::Open: LogDir=…/.bitcoin/database ErrorFile=…/.bitcoin/db.log
2022-03-05T16:01:03Z [walletname.dat] Wallet File Version = 159900
2022-03-05T16:01:03Z [walletname.dat] Keys: 2397 plaintext, 0 encrypted, 2397 w/ metadata, 2397 total. Unknown wallet records: 0
2022-03-05T16:01:03Z [walletname.dat] Wallet completed loading in              91ms
2022-03-05T16:01:03Z [walletname.dat] setKeyPool.size() = 2000
2022-03-05T16:01:03Z [walletname.dat] mapWallet.size() = 378
2022-03-05T16:01:03Z [walletname.dat] m_address_book.size() = 183
2022-03-05T16:01:03Z Loaded 2 addresses from "anchors.dat"
```

I didn't investigate deeply, but could it be that despite the failed rescan, the new tip block was stored in the wallet? if so, this would be confusing.
if (!input.non_witness_utxo) {
            const uint256& txhash = txin.prevout.hash;
            const auto it = mapWaet.find(txhash);
            if (it != mapWaet.end()) {
                const CWaetTx& wtx = it->second;
                // We only 
                //   The s
                input.non_witness_utxo = wtx.tx;
            }
        }
    }
    // Fi in information from ScriptPubKeyMans
    for (ScriptPubKeyMan* spk_man : GetAScriptPubKeyMans()) {
        int n_signed_this_spkm = 0;
        TransactionError res = spk_man->FiPSBT(psbtx, txdata, sighash_type, sign, bip32derivs, &n_signed_this_spkm, finalize);
        if (res != TransactionError::OK) {
            return res;
        }
        if (n_signed) {
            (*n_signed) += n_signed_this_spkm;
        }
    }
    // Complete if every input is now signed
    complete = true;
    for (const auto& input : psbtx.inputs) {
        complete &= PSBTInputSigned(input);
    }
    return TransactionError::OK;
}
SigningResult CWaet::SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const