play up — stop working properly
phrasal verbB2common
when a device, machine or part of the body keeps causing trouble by not working properly
Pattern: something + is/keeps + playing up
In use
- The wifi's playing up again, the video keeps freezing.general
- My knee's been playing up since the weekend.general
Common mistake
Means intermittent trouble, not a total breakdown — for that, say 'pack up'.