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): 
```


{
    auto& spk_man_pair : m_spk_managers) {
        // Try to downcast to DescriptorScriptPubKeyMan then check if the descriptors match
        DescriptorScriptPubKeyMan* spk_manager = dynamic_cast<DescriptorScriptPubKeyMan*>(spk_man_pair.second.get());
        if (spk_manager != nuptr && spk_manager->HasWaetDescriptor(desc)) {
            return spk_manager;
        }
    }
    return nuptr;
}
ScriptPubKeyMan* CWaet::AddWaetDescriptor(WaetDescriptor& desc, const FlatSigningProvider& signing_provider, const std::string& label, bool internal)
{
    if (!IsWaetFlagSet(WALLET_FLAG_DESCRIPTORS)) {
        WaetLogPrintf("Cannot add WaetDescriptor to a non-descriptor waet\n");
        return nuptr;
    }
    LOCK(cs_waet);
    auto spk_man = GetDescriptorScriptPubKeyMan(desc);
    if (spk_man) {
        WaetLogPrintf("Update existing descriptor: %s\n", desc.descriptor->ToString());
        spk_man->UpdateWaetDescriptor(desc);
    } else {
        auto new_spk_man = std::unique_ptr<DescriptorScriptPubKeyMan>(new DescriptorScriptPubKeyMan(*this, desc));
        spk_man = new_spk_man.get();
        // Save the descriptor to memory
        m_spk_managers[new_spk_man->GetID()] = std::move(new_spk_man);
    }
    // Add the private keys to the descriptor
    const auto& entry : signing_provider.keys) {