We use Vapotherms a lot. Not many problems now; the ones we had initially, we got to know cures for, eg:
1. Check the circuit is properly pushed together and properly pushed into the device,
2. If strange temp faults occur, take the circuit out, give it a shake and put it back - may be an air bubble over the temp sensor, and
3. They don't like being stopped and restarted. If the patient comes off for a while, turn the Vapotherm down not off.
I hope this helps!