MS Paint transparency problems.

good day, i haven't ever used this website, so i apologize for any mistakes.

i've been having this problem for quite a long time, as well as my friends - and i had seen that a couple other people had it too. i never saw a solution to it.

namely, the transparency selection tool sometimes doesn't work, randomly.
even having the same colour as the background in the secondary colour picker, it will still not work.
it's very random. it works most of the time, and then it doesn't. sometimes to fix it you have to just turn it on and off and on and off a couple of times, and while it works for a while, it later once again happens, and it's so tedious.

does anyone have any idea what problems might be causing it?