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
```
AssertLockHeld(cs_main);
    
    
    
    LOCK(pool.cs);
    assert(!tx.IsCoinBase());
    for (const CTxIn& txin : tx.vin) {
        const Coin& coin = view.AccessCoin(txin.prevout);
        
        
        
        
        if (coin.IsSpent()) return false;
        const CTransactionRef& txFrom = pool.get(txin.prevout.hash);
        if (txFrom) {
            assert(txFrom->GetHash() == txin.prevout.hash);
            assert(txFrom->vout.size() > txin.prevout.n);
            assert(txFrom->vout[txin.prevout.n] == coin.out);
        } else {
            const Coin& coinFromDisk = pcoinsTip->AccessCoin(txin.prevout);
            assert(!coinFromDisk.IsSpent());
            assert(coinFromDisk.out == coin.out);
        }
    }
    return CheckInputs(tx, state, view, true, flags, cacheSigStore, true, txdata);
}
static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool& pool, CValidationState& state, const CTransactionRef& ptx,
                              bool* pfMissingInputs, int64_t nAcceptTime, std::list<CTransactionRef>* plTxnReplaced,
                              bool bypass_limits, const CAmount& nAbsurdFee, std::vector<COutPoint>& coins_to_uncache, bool test_accept) EXCLUSIVE_LOCKS_REQUIRED(cs_main)