I think that if a reorg fails due to an error while disconnecting blocks, the node should shut down.

My thought is that if we are trying to switch to a more work chain and something goes wrong before we can even try to validate that more-work chain, then we have a problem that is not related to the chain we're trying to switch to but instead related to our own hardware or software; shutting down and having the user deal with the issue is better than continuing on, when we know there's a more work chain that we're unable to try validating.

This has recently come up on testnet, where unpatched nodes are unable to reorg from the invalid chain containing the duplicate-input-in-a-transaction block, but rather than crash or shutdown they are continuing on the invalid chain, with messages like this in the debug log:

```
ERROR: DisconnectTip(): DisconnectBlock 00000000210004840364b52bc5e455d888f164e4264a4fec06a514b67e9d5722 failed
```
return true;
        }
        
        for (CTxMemPool::txiter it : allConflicting)
        {
            LogPrint(BCLog::MEMPOOL, "replacing tx %s with %s for %s BTC additional fees, %d delta bytes\n",
                    it->GetTx().GetHash().ToString(),
                    hash.ToString(),
                    FormatMoney(nModifiedFees - nConflictingFees),
                    (int)nSize - (int)nConflictingSize);
            if (plTxnReplaced)
                plTxnReplaced->push_back(it->GetSharedTx());
        }
        pool.RemoveStaged(allConflicting, false, MemPoolRemovalReason::REPLACED);
        
        
        
        
        
        bool validForFeeEstimation = !fReplacementTransaction && !bypass_limits && IsCurrentForFeeEstimation() && pool.HasNoInputsOf(tx);
        
        pool.addUnchecked(entry, setAncestors, validForFeeEstimation);
        
        if (!bypass_limits) {
            LimitMempoolSize(pool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
            if (!pool.exists(hash))
                return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "mempool full");
        }
    }