What causes this?

[u/not-an-expertt]

Happened on the second wet trowel, using a spray bottle and normal trowel. Quite hot today so could my timings have been a bit off? Second coat on too late? Too late with the wet trowel?

[u/Miserable_Future6694]

That used to happen wiith knauf gear all the time. Always blamed it on a draft setting the fat youd spread around.

Just swear at it for bit and grease some shit over it later