Had the seat problem happen on a Caravelle. Brief pitch up before the PIC released the controls and FO took over. Not fun.
Re flaps,
locked up, I'd fly it home or to the next maintenance if practicable, that is if the maintenance is based on field of the increased runway lenght I'll need. Most SEP's are very easily flyable flaps up.
partially extended such as in take off position it would strongly depend on the distance to fly. 90% of the time it's RTB, if it's a 50 mile leg to homebase where the engineering is, I'd probably go on.
Re RTB:If you're in Italy, think again
might become expensive. Which might lead someone to NOT RTB and crash. That is why Italy is off my list for now.