Did you create the blueprint in 0.15.13, save it, and then change mods?
Because loading a save from 0.15.12 (or blueprint storage from 0.15.12) directly while changing mods will still have the problem as the save data required is not in the old versions.
If you want to get ahold of me I'm almost always on Discord.
Okay, I just re-saved the two maps to 0.15.13-3 map version and tested again. Same problem :/ I am loading up creative mode and going to try with two new maps and see if it still happens.
Okay, going from a new map to a new from 0.15.09 (and upgraded to 0.15.13-3) works So it might just be the old map I am trying to save from. I would say it is fixed but this is a fringe issue probably with my old map.