If I understand you correctly: I think I had the same issue once when I tried Native Instruments Super8 Synthesizer with one of my Midi controllers (I think it was Launchpad X). I learned that some controllers send note-off (0x80) messages and others are sending note-on (0x90) messages with velocity “0” on note end. Most instruments might understand both, but in my case it wasn’t the case for Super8.
This might be related here, but I don’t know. Just as possible additional context.
Edit: Probably this is also connected? Strange sustain behaviour in Zynthian?