Thank you for your reply.
The first four png-files that aren't exporting properly are all spritesheets containing 16 rows and columns. The total sprite dimensions are 2560x2560 which sounds like a power of 2 to me.
The other 15 png-files that aren't exporting have all sorts of odd dimensions such as 58x53, 64x53, 45x51, 16x12 and 13x10 for example.
My sprites are not set to repeat nor using mipmaps.
Exporting to PC or macOS works just fine. I have had no issues whatsoever.