This is similar to #21352, #20270, #18831, #18161, but they have all been closed/fixed, and this is happening again on master as of the [last CI run](https://github.com/bitcoin/bitcoin/runs/2928080250):
```bash
122/210 - feature_backwards_compatibility.py --descriptors failed, Duration: 68 s
stdout:
2021-06-28T03:28:48.903000Z TestFramework (INFO): Initializing test directory /tmp/cirrus-build/ci/scratch/test_runner/test_runner_₿_🏃_20210628_031620/feature_backwards_compatibility_97
2021-06-28T03:28:52.381000Z TestFramework (INFO): Test wallet backwards compatibility...
2021-06-28T03:29:56.399000Z TestFramework (ERROR): JSONRPC error
Traceback (most recent call last):
  File "/tmp/cirrus-build/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/test_framework/test_framework.py", line 128, in main
    self.run_test()
  File "/tmp/cirrus-build/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/feature_backwards_compatibility.py", line 110, in run_test
    self.nodes[1].abandontransaction(tx3_id)
  File "/tmp/cirrus-build/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/test_framework/coverage.py", line 47, in __call__
    return_val = self.auth_service_proxy_instance.__call__(*args, **kwargs)
  File "/tmp/cirrus-build/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/test_framework/authproxy.py", line 146, in __call__
    raise JSONRPCException(response['error'], status)
test_framework.authproxy.JSONRPCException: Transaction not eligible for abandonment (-5)
2021-06-28T03:29:56.453000Z TestFramework (INFO): Stopping nodes
2021-06-28T03:29:56.723000Z TestFramework (WARNING): Not cleaning up dir /tmp/cirrus-build/ci/scratch/test_runner/test_runner_₿_🏃_20210628_031620/feature_backwards_compatibility_97
2021-06-28T03:29:56.724000Z TestFramework (ERROR): Test failed. Test logging available at /tmp/cirrus-build/ci/scratch/test_runner/test_runner_₿_🏃_20210628_031620/feature_backwards_compatibility_97/test_framework.log
2021-06-28T03:29:56.724000Z TestFramework (ERROR): 
2021-06-28T03:29:56.725000Z TestFramework (ERROR): Hint: Call /tmp/cirrus-build/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/combine_logs.py '/tmp/cirrus-build/ci/scratch/test_runner/test_runner_₿_🏃_20210628_031620/feature_backwards_compatibility_97' to consolidate all logs
2021-06-28T03:29:56.725000Z TestFramework (ERROR): 
2021-06-28T03:29:56.725000Z TestFramework (ERROR): If this failure happened unexpectedly or intermittently, please file a bug and provide a link or upload of the combined log.
2021-06-28T03:29:56.725000Z TestFramework (ERROR): https://github.com/bitcoin/bitcoin/issues
2021-06-28T03:29:56.725000Z TestFramework (ERROR): 
```


AddToSpends(hash);
    const CTxIn& txin : wtx.tx->vin) {
        auto it = mapWaet.find(txin.prevout.hash);
        if (it != mapWaet.end()) {
            CWaetTx& prevtx = it->second;
            if (prevtx.isConflicted()) {
                MarkConflicted(prevtx.m_confirm.hashBlock, prevtx.m_confirm.block_height, wtx.GetHash());
            }
        }
    }
    return true;
}
bool CWaet::AddToWaetIfInvolvingMe(const CTransactionRef& ptx, CWaetTx::Confirmation confirm, bool fUpdate)
{
    const CTransaction& tx = *ptx;
    {
        AssertLockHeld(cs_waet);
        if (!confirm.hashBlock.IsNu()) {
            const CTxIn& txin : tx.vin) {
                std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range = mapTxSpends.equal_range(txin.prevout);
                while (range.first != range.second) {
                    if (range.first->second != tx.GetHash()) {
                        WaetLogPrintf("Transaction %s (in block %s) conflicts with waet transaction %s (both spend %s:%i)\n", tx.GetHash().ToString(), confirm.hashBlock.ToString(), range.first->second.ToString(), range.first->first.hash.ToString(), range.first->first.n);
                        MarkConflicted(confirm.hashBlock, confirm.block_height, range.first->second);
                    }
                    range.first++;
                }
            }
        }
        bool fExisted = mapWaet.count(tx.GetHash()) != 0;