For sure it depends on the hardware encoder being enabled on the server side (it can’t be reproduced with software encoding), but we suspect that also the specific decoder in use could help to trigger the issue.
Are you connecting from a Windows client? I this case, would you try the following?
1. Re-enable hardware encoding on server.
2. Then download dlls from:
(or alternatively go to https://ffmpeg.zeranoe.com/builds/ then select 4.2.2 + windows 32 + shared and download build).
3. Go to Nomachine installation directory on client machine (e.g. C:\Program Files (x86)\NoMachine\bin) and rename libav.dll to libav.dll.backup (or similar).
4. Extract ffmpeg-4.2.2-win32-shared.zip and copy these files:
avcodec-58.dll, avutil-56.dll, swresample-3.dll
to Nomachine installation directory.
5. Run the NoMachine player and try to reproduce the issue.