I found several posts about this issue in the Unifi forums - some a few years old, some newer.
Seems to be a rare problem but you're not alone.
I don't use that software so I can't tell you much but I would try what the UI-Team person suggested in this thread:
Take a settings only backup and reinstall the controller.
If that doesn't help I would suggest you post your question again at the Unifi forums.