Quote:.. Any more suggestions?..
(Without better information as to number of layers, workflow ...why and wherefore)
Quote:it's this size 5199x5040
That is quite a large image. Do you need to retain the layer with layer mask ? Can you perhaps duplicate the layer+mask and apply the mask. Then rotate that new layer. If you have lots of layers, maybe drag the new layer out to make a new 1 layer image and rotate that. Then drag back into the main image.