Ceiling paint cracking

Help! I really cannot fathom what's going on with my ceiling. It's a mixture of old plaster, a bit of new plaster and some filler. I sanded any glaze off and mist coated with a 10% dilution and it immediately started bubbling in a few places. Once dried, it started crazing/flaking in isolated areas. So I removed all the flaking paint, sanded back to the bare surface, put on a couple of coats of Zinsser Peel Stop, filled the sanded areas and sanded flat to the surrounding surface, applied two more coats of Peel Stop and re-misted. Mist coat looked ok so did a coat of undiluted emulsion and it's blistered and crazed again. What on earth is going on? Is my only hope to use lining paper now? Any thoughts will be much appreciated.

Years ago people bought a powder and mixed with water and brushed on ceilings. White wash. It's why people say wash the ceilings white or they might say wash ceilings and I want walls painted.
Its like chalk and you can wash it off with sponge and water to remove as nothing sticks to it. Anything before 1950s ish could have its on.

Overboard or get it off back to plaster.

Distemper was another that came in around the 1940s in just a few colours and good for walls and did not brush off on your clothes. Distemper is now degrading and again nothing sticks to it so well. I sand that off and apply gardz or similar to seal.

I guess you have one of these on you ceiling and any damp causes the filler ect to come away. Nothing you put over will be a long term fix...

Thanks for the reply. It's an under-stairs ceiling with 1/4 returns so sloped in two separate directions. I think I'm better off pulling it down and starting afresh rather than overboarding. Bu99er