Did I get it right that when you import a photo (created with the device camera) to Lr Mobile, make some edits and save it back to the camera roll that you're getting a downsampled photos? - Guido
Sorry, should've made that clear. No, these are DSLR shots that were imported to/edited on LR desktop, then synced to mobile.
I see. Shots synced from Lr desktop do not have the full resolution size. Lr Desktop uploads smart previews to the back-end. Only photos imported from a mobile device to Lr Mobile do have the full resolution at the back-end. Currently you can only share photos with a full resolution size which have been imported to Lr Mobile from the camera roll on a mobile device. Is that what your are seeing?
No, that's not what I'm doing.
This is my workflow:
Edit DSLR shots in LR Desktop
Sync to mobile
Save to mobile camera roll
Weirdly, this problem seems to only be happening to a roll of shots I took over a single weekend. Since that batch of shots, all pictures saved to my mobile camera roll have been fine.