Upstairs toilet leaking into ceiling
Common problem, you have unfortunately been cursed with a series of maroons since fixing a leaking toilet is about the easiest handyman job there is.
My guess is you could do a better job fixing it than the buffoons.  Turn off the water, wipe up all the drips and such behind the toilet so that everything there is clean and bone dry, then turn the water back on and lay back with your head behind the toilet for 20 minutes staring at the plumbing.  Eventually you will see a little bead of water forming somewhere that is where the leak is.  My guess is it's the valve stem seal but there's plenty of other potential areas.  Feel around on the pipes with your fingers.  Water leaks like to happen behind pipes and such where you can't see them and water likes to travel down away from the actual source to make it harder to find the leak.  You can't find these leaks by just staring at pipes you have to get your fingers in there and feel around.