I've found that one area of a wall will work great, another will need a bit more TLC. While I love plaster for its character and solid feel, I do not like it for ceilings. I worry about the previous owners not taking care of it and letting it get wet when there were leaks. This weakens it greatly. I've had it disintegrate over me while working up there sometimes. My home has drywall ceilings, now.
It may be that your plaster was simply "shot." Ceilings have to contend with gravity, vibrations from above, changing temperature if below an attic, and a whole host of other things.
The plaster washers do a good job when there are a few things in place:
1) Plaster is otherwise sound, but may have bowed or have a crack in it 2) lathe, while not necessarily attached ot the plaster, is in good shape and present behind the plaster. 3) There are studs or joists nearby to anchor at least one or two plaster washers (along with the ones anchored to the lathe).
I also find that sometimes I'll need longer drywall screws for certain applications. While working on a drywall over plaster ceiling the other day, I neede 2 1/2" screws as 1 5/8" weren't going to cut it.
I use a variable speed drill and go slowly with the plaster washers and screws. Too fast will drive it through the plaster sometimes. It also will tear up the base coat of plaster and undermine the area.
But then again, sometimes plaster is damaged beyond repair by moisture and the elements.