It's barter related, ran into the same issue a few times. I've used packmule/str Jahan as a crafter, he didn't lose a single item my entire run. The few occasions I've accidentally traded with him he gained a few hundred gold and lost a ton of items(carrying capacity down from something like 700/750 to 400/750). Same with the rejoining henchmen, they lost the majority of potions and scrolls carried whenever I clicked trade but no problems otherwise.
Dumping all the materials and 3 barrels on a crafter will save you a ton of annoying micromanagement, just always save on arriving at the hall of heroes in case you misclick.
