Yeah I’m starting to think the flap problem is unique to my unit. Puzzling, since optically there seems to be nothing wrong with it.
As mentioned in the review, I already found the workaround. I opened threads for Pico-8 and TIC-80. But I appreciate you sharing it anyway. 
I was all set up to build TIC-80 myself but then the CM3 unit arrived and I never got back to it. I should give it a go!