I'm not sure, legally, how you'd stand in the event of a failure. I'm sure that you've excercised a reasonable duty of care, and as a consequence can't be held responsible
soak down the bare spots with primer L (Mapei) mixed with water 50/50
use luke warm water and a spritzer and soak it good so it goes throught the bare paper into the plaster.
If it bubbles as it is drying anywhere just lightly apply some pressure when it has flashed the water out (hard to say how long that will be, but don't be too quick about it).
Primer L is pressure sensitive and bubbles will lay down once it has flashed off.
That stuff really sticks. damn hard to get off if you get it on painted or wood surfaces and let dry so make sure you use a drop sheet and clean up any drips and overspray immediately.