For some reason i am not able to export 4096 textures. On export there is a brief progress bar, but no file output.
This only happens with certain Roughness textures
These textures are part of LuosCave pack. It was no problem to export other 4096 textures of this pack.
Images tested are in PNG format
File size is around 24mb
This might be due to the files are in PNG format, but Unreal Engine seems to be unable to export PNG (or convert to TGA), upon exporting.