Plasterboard cracked near wall

[Northy1]

Hi,

We had the attic converted about 13 years ago. They dropped the ceilings in the bedrooms and replastered.
I've noticed that the plaster near the window seems to have dropped and cracked away. I'm wondering if anyone could advise me as to what might be going on here?
Thanks for your time

 

[Wayners]

No corner tape between the wall and ceiling will not help.
Seen a few like that with building debris sat on other side of board causing board to drop over time.
Is there a joist near that edge?
Magnet will pick up screw heads that hold plasterboard to joist or you can tap tap and listen for the solid noise of joist vs hollow noise with nothing behind.
If it's dropped then weight and lack of fixing maybe cause over time.

 

[Northy1]

I've been looking at it worrying that the ceiling is going to collapse or something. That's reassuring. Cheers.

 

[Northy1]

Yeah, I think there probably is a joist around there- I couldn't honestly tell you though.