So a couple of years back we had a professional repaint our ensuite.
A few months later bubbles began to form in one area slightly away from the shower, on the ceiling. It got worse and spread, until it popped.
We contacted the painter, who after a very long time, came back recently to repaint.
Paint is bubbling again in the same area and it's only been a couple of weeks since he did it.
We didn't see what he did to "fix" the original issue, but our concern is that perhaps both times he didn't prep the ceiling. This is our unqualified guess.
What other reasons could there be?