We have one of these: [[Cat Mate C500 automatic pet feeder]]
It started going into an infinite spin. (Which drove [[Enid]] a bit mad!)
Thanks to this very helpful video Fixing Cat Mate / Closer Pets Automatic Feeder (Infinite Spinning), I learned that usually all you need to do is clean the sensor.
I did, and it worked fine again.
Handy tip also about holding ADJ + UP to make it spin to test it, and to realign it if it’s gotten misaligned.