Honestly I think you're just doing it wrong. Messing with PDF's is probably one of the coolest built in features I know of, and with Markup etc in Preview it's super easy.
Be careful of PDF's with built in broken fields though, in which case I just add a text field on top if it's easier.
You see this pattern a lot around Apple users where they insist there simply can't be bugs in Apple software. It's really counterproductive and it's part of the "crazymaking" element of interacting with Apple software and Apple's fanbase.
There should be nothing "wrong" I can do which makes text disappear which can't be undone, or where the click-and-drag targets are as tiny as can be.
The program is buggy. Apple releases bad software sometimes. That is simply all there is to it.