You can try to send the command “hasnodefailed” with mqtt, and after that, send a “removefailednode”
Simply go to the mqtt-integration and send a packet to the topic
OpenZWave/1/command/hasnodefailed/
With the payload
node: X (where X is your node id)
And after that, send the same
OpenZWave/1/command/removefailednode/
With the payload
node: X
That managed to remove a couple of my faled nodes, but not all of them, unfortunately…