I often have similar artifacts and I always use only one texture file, so that shouldn’t be it.
It seems to me that it might be caused by difficult areas, I encounter it in deep recesses, where I cannot take ideal images. Could you upload a clay render so one can see if there are any alignment issues?
not clear if you got visible seams on the printed part or on the printer software. Anyway I also got same visible seams on the printed part once I printed a PLY file (the Projet 660 does not accept OBJ), when RC was not even existing yet.
Convert the model to WRL and the issue should disappear.