acts up, malfunctions, messes around, fools around
Putain, il déconne ce truc ou quoi ?
Damn, is this thing messing with me or what?
— Alien, le huitième passager (1979)
My typewriter is acting up.
The coffee machine is malfunctioning.
Je commence à sentir que quelque chose déconne.
I'm starting to feel like something's going wrong.