I don’t know if this is your issue or not, but it’s one thing worth looking at.
If you’re on Windows 11, chances are Windows put your user profile on OneDrive. If NT is using the Documents folder on OneDrive, this could cause many many issues. Either remove OneDrive or find a way to point NT user profile to your local drive C:\users\YOUR_USERNAME\Documents.
Also the following might help.
https://ninjatrader.com/support/helpGuides/nt8/performance_tips2.htm
Good luck.