REgal guy: Get real, all the guessing in the world won't solve your problem. Someone left something loose, mis-assembled or you are the unluckiest guy on the planet. The cover has to come off and good trouble shooting take place. If you do it you are leaving the mechanic who did the job off the hook, your decision. TAKE IT BACK AND MAKE THEM DO IT RIGHT. I made my living as a scooter wrench for over 40 years, some times you screw up, if so I wanted to make it right. My rep was my bread winner, and I lived good and stayed busy.
YMMV