That sounds more like a Stadia specific bug, that might warrant its own thread, if you're still having that problem.
It likely is a Stadia specific thing, and yes I do still have it. I've tried with several different classes and builds and play all of them regularly. None have advanced beyond level one, and more vexing is that sometimes the progression bar gets close to rolling over and then the next time that you check, oops ..... all gone and still level one.
Stadia has no support themselves and bringing it to their attention earns you a suggestion to tell Larian about it .... rinse and repeat!
