Thanks for replying!
this works, BUT it won't work in a situation where the top object is moving, for example sliding on top of the bottom object, because in this case it will stop. i could perhaps store the velocity X + Y in variables to circumvent this, but i would like to have a bit more unintrusive way to do this. basically letting the top object just mind it's own business, intact, whatever it is doing on top of the bottom object.
is there any other way to refresh the collision?
(i did find another way around this: make a second animation frame for top object, shrink the collision box just a tiny bit, then set the frame after (or before) disabling collision. it works but again, it is kinda hacky method, and i would still like the top object be intact, in its original form)