I know it’s a known bug that the Slot machines will spin indefinitely. However I encountered it twice on a slot(s) i was occupying and i believe i have found a possible cause, and have accidentally reproduced it later
I went AFK on a slot and as the timer hit 0 i realised and hit a button, in doing to it both kicked me out of the chair and spins the slot. The slot spins infinitely because you are no longer its owner. re-occupying it will lock you in and you cannot interact with it / get out of the chair.
I hope this is a help