pk3ds Pokemon UltraMoon Pk3ds can't rebuild

[bobertdps4]

I'm trying to make a rom hack of Pokemon Ultra Moon, with all battles changed to double battles and some minor buffs to weak pokemon. I extracted the files using pk3ds and changed the stats and abilities of some pokemon and I also increased the shiny rates. But now, when I try to rebuild the ROM, after a while of loading it says An unhandled exception has occurred before closing pk3ds entirely. Does anybode know what might have happened and what I can do about it?