Hi.
Apparently there is an ongoing unresolved issue with Sims 4 Cats & Dogs Expansion Pack. - This issue been mentioned probably since 2018.
The issue is: After claiming a perk in the vet clinic, specifically the vet coat (full outfit vet coat). The sims are unable to wear the uniform during their shift.
After correctly setting the uniform as the work attire for the vet clinic (both employees and my personal sim) will change to random clothing to perform work actions.
I hope this issue is resolved as soon as possible. If you don’t mind, you can also research on google the same issue others been experiencing for years and still nothing to this date.
@Ella033 there's a link here to the bug report if this is the same issue that's affecting your game, if you want to click Me Too on the first post and add your bug report if you'd like to as well:
