In my experience the odds strongly favor a network communication issue that could be uncovered with a Zniffer. However, the network health function of the PC controller might help. Here is an earlier version of mine (green means good communication)
However, one question I haven’t asked (and I don’t see in your posts) is what are you running OH3 on? There is a known issue with some early versions of the Aeotec Zstick with a Rpi4 that requires using a USB hub (doesn’t have to be powered) between the Rpi and the stick.
I don’t have that issue, but use a powered hub for the zstick anyway, so the zwave radio is always getting steady power, rather than rely on the Rpi power. I find that helps communication.
Lastly, you might want to review this post for other ideas.
Bob