Same issue here. If you uninstall the feeder and reinstall it then the button starts working.

Uninstalling doesn't work
then were working for me like normal I still ahve two i can still adjsut but now the ones I'm making cant be adjusted very frustrated

Just a stupid question, but worth a shot nevertheless. Have you tried to dump the meals laying on the feeder and then increase the number? Tho you have to be fast, doing so ;)
Other approach would be, to place a valve in front of the feeder-pipeline so you can do it easier.

Same issue here.

same

No matter what I do with the stack size buttons, it always and only ever spits out stacks of 10.
On top of that, if there's a stack of veggie paste on the thing and then meat gets added to the mix, as soon as I take one meal the vat dumps its entire contents on the ground all over the place.
I'm guessing it tries to drop a stack of 10 on the stack of 9, they can't be stacked because it's veggie and meat, and it slides off onto the floor. And then it just keeps trying til the vat's empty.
Very strange behavior.
I won't be using feeders for now.