Bertie Tomy keeps squeaking

I opened up Bertie because he was moist inside thinking the battery was leaking but it seems to have just been lots of grease. Now i have put it back together it runs but sqeaks loudly. All the gears are ok but perhaps the one closest to the switch is not sitting right on the drive wheel. A youtube video mentioned the switch position as an issue why you shouldnt open his gearbox but i saw it too late. Here is a video. From Tomica World set 7408J. https://youtube.com/shorts/Omv9Ik5FJ4Q?feature=share

Getting the gear and on/off switch to fit nicely back together is vexing (at least for me). I’m not sure why it would be squeaking, but can you tell whether the on off switch is toggling as smoothly as before you opened it? If it isn’t then I suppose it could be slightly askew and that misalignment could cause the cog to squeak? ¯\_(ツ)_/¯

[Super]

I didn't hear a 'squeak' in the video. Quick question: What are the front wheels moving?

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.

[Super]

Its hard to know when we can't see what the inside looks like but it definitely sounds off.