FeedMyData wrote The legs texture had a max size of 2048 when all the others had a max size of 4096. Putting the same setting everywhere fixed the issue. My bad, thanks!
Glad to hear you've figured it out! Do you mean that the original file size is 4096 and it was set to Max Size 2048?
If so, then this would most likely be due to this known bug in Unity. The ticket says it's fixed in 2020.1 (in March last year I received a mail claiming it's fixed in 2020.2, so at least there it should be).
Edit: is it best practices to always tick Read/write enabled? Or can I ignore this setting as long as everything is working fine.
For any atlas page textures that need to be combined at runtime, this is required, yes.
We already have a checklist for potential problem causes when combining skins at runtime on the spine-unity documentation pages:
spine-unity Runtime Documentation: Combining Skins
On a similar topic, we are not using rotation when exporting textures from spine. When we repack them in Unity, we sometimes have images that are cropped. Is it a known limitation or are we messing up something this time too? (I can open a new topic if you prefer)
Regarding the cropped images, do you receive half or quarter sections (in contrast to arbitrarily cropped sections)? If so, then this should be due to the above bug with half or quarter resolution texture settings (either in Quality Settings, then check out the active quality tier, or via max texture resolution). Could you please check these settings as well? If not, could you please post a screenshot showing the cropped image?
In general, if using Unity versions earlier than 2020.1 with the known bug, then you should make sure that any repacked textures are not resized down due to Quality Settings (half or quarter texture resolution) or via Max Size.
