Bertie Tomy keeps squeaking

Thanks for your replies. I reopened it since posting and the front wheels no longer move can't explain that as they are supposed to roll free. Perhaps the motor was vibrating close to them. The sound is more like a rubbery squeak like the rear wheel was rubbing on the drive cog. It seems to be working a bit better now but still feeling like everything i open up and clean runs worse. My Terrence's switch sits more definitively to one side than this bertie i dont remember how ir looked before i opened. The plastic joining the switch to the drive cog fell off before i could take a photo but im sure it is in the right general spot. Again thanks for the help.