I’ve a lot of experience with paints even if I’m not a painter, painted walls in my houses so many times for myself and friends, did venetian plaster, and did antiques furniture restoration as a hobby since I was 18 (60 now).
My first thought looking at the pictures is exactly what @muth said, reaction, acrylic over “something else” probably oil or chemical paints.
Paint can be as expensive as you want but where is the paint gong to stick to?? Oil??
Prime is a must and a good one too! That’s why @muth said ask the techs.
What do you need to do? Renovating and look new? Simple answer, sand it down… completely! Anything else it’s not going to make it look perfect, then, wash it and clean it thoroughly (no dust!), prime and paint.
If you need just to patch it up, looking at your pictures, before any primer you’ll need to sand the cracks, bubbles or whatever, as far as they go (otherwise they’ll open up again) as @SessionDrummer said, I’d use a wood filler and sand everything even, then, you can wash, clean, prime and paint.
From my point of view (but it’s a Restorer point of view…) I’d try to sand it down (I know it’s a lengthy process) as much as possible and do it all up again, by the look of it, it’s already been patched up a few times… so you just might as well, then clean, prime, paint and add a final hand of transparent finish with one of those (expensive) transparent UV rays wood protection paints but it’ll save you time in the future, you won’t touch it again for years.
Done it in my house years ago and never touched the wood beams again and I’ve got a lot of them…