I’m wondering on any progress on this issue.
I see the exact same issue on my Mac Studio M1 Ultra running macOS 15.0 Sequoia. Reverting to a prior version (8.4.2_5 … it’s the latest before current that I have an install for LOL) resolves the issue for me, but the prior version is old enough that it has it’s own issues … just not “bad message” ones!
The firewall is not the issue, and my Intel laptop & linux machines all work fine with the latest NoMachine version … just this specific macOS computer!
Might be an interesting data point. Thx for your help!