Scrape off the painting of bathroom celling
Gyprock ? Is that a name for Sheetrock? If so moisture above could be a problem even if properly sealed and painted.

The year of construction would be helpful also. Green /blue board are forms of water resistant Sheetrock, as the lighting level is low I cannot tell but it may be green board from my best guess.

Many bathrooms that do not have proper ventilation have issues with ceiling paint even with the best preparation every type of wall board can have issues as the moisture if not exhausted can cause bubbling, mold and many other problems.