I am having this exact problem! It is really frustrating, as soon as i pick a career path, every day after getting the performance bar to Good or Excellent, it resets to average. i spent about 2 hours trying to get it higher before i realised it was resetting.
I haven't played for months, and now trying to get back into it, getting this issue is really frustrating because i cant progress in any career at all. i tried switching careers, and same problem. I complete the tasks, i get raises regularly, never get promoted
Have seen some people say it appears to be linked to "entrepreneurial trait" but my sim doesn't have this trait, nor do i even see it is something i can choose for any of my sims - i do not have that many expansion packs and i think from googling that trait comes from an expansion pack? i did have Genius trait on however and i did try taking that one off just in case, but still same thing happened - Performance bar rests to Average and cannot progress. Currently the only trait i have equipped is "loves outdoors". I have also tried changing Aspirations, and still performance resets from excellent to average by the time sim next goes to work. it does not decline back down, it just jumps. I have tested leaving the Job tab up to see and it just jumps back down to Average a few hours after she gets home