Paint peeling in shower room

[bawbster]

Few months back wife decides it's time for the en suite to be painted again, used the usual Dulux bathroom paint as have done the previous 3 or 4 times it has been done. This time though, the paint has started to crack and peel. Sanded off the cracked paint (didn't fill it) repainted and it's happened again. I've always painted over the previous paint with no issues but obviouslt this time there is. The window is always open and the extractor is always on for a shower and left on for a few minutes after.

Other than scraping and sanding, what can I do to prevent this from happening again?

Cheers

 

[Wayners]

Condensation.
Run a dehumidifier outside for a few hours every evening to dry out.
Extractor and opening windows helps but won't fix

 

[bawbster]

Condensation.
Run a dehumidifier outside for a few hours every evening to dry out.
Extractor and opening windows helps but won't fix

Any idea why condensation would cause this after all this time?

 

[foxhole]

Opening window cools room which needs to be warm long enough for fan to do its job.So no surprise it’s bad over the window?