SOLVED Some sprites and text started to be drawn permanently.

Hello, first time posting. I've encountered a weirdest problem and have absolutely no clue what caused it.

After some work with completely unrelated stuff i've noticed that, in some cases, sprites and text are drown over previous sprites and text, which should've been gone by the end of the step. And what's even more puzzling, i haven't modified objects responsible for those drawing events in a relativly long time.

In addition to that, simultaneously randomize(); function stopped working, and each time i restart the game or room, nothing in randomized values changes. I would assume both of those issues have the same cause, but after spending hours trying to figure our the reason, i finally gave up and decided to ask for help. I can provide any additional information, including code, if that would help. Here's youtube link to show exactly what happens:

Thanks in advance.
do you have a visible background in the room with a color selected or a picture on it with no transparency?
Well, this is kinda embarrassing - turnes out i accidentally made background layer in this room invisible, and turning it visible indeed solved this problem.
I cannot thank you enough - probably would've spent hours upon hours trying to figure this on my own.