thank you for your reply :)
yeah trying to figure things out my self , since it's not the first time this kind of weird stuff happens,
i have the latest firefox 80.0.1 right now
sadly there are no more information on the web about this problem
similar problem is in game created by google (pangoline love , the 2017 valentine day game) , so it's more weird since they should know their stuff (well except they and firefox are still in browser war), there it happens on moving character but not on the background , and more weird thing is , that on older firefox (don't know the version) it worked without problems , but the bug appeared years later in newer version
some other game (forgot the name) there it happened in 3D canvas so *weird stuff*
but normal javascript canvas work normally , or even WebGL 1 works fine
also could be something in the mix of canvas => graphic drivers => graphic card , hard to say am not a good at this stuff,
but that's just hypothesis that i can't confirm or deny :/
(i got build in intel GPU from 2008 and windows 7 home edition 64bit ) if this info helps anyone,
only solution at this time for me was to change browsers , even just for this game :) most people have more then one browser anyway XD
BTW > you game is awesome :) got in to it on Vivaldi browser
also one thing i noticed , is small stuff , when entering the lift on right side of the door it only opens the right side , but if open the lift on left side it opens both doors the normal way
anyway great game keep up the great work :), wish You a lot of happy players :)