Hello. I'm currently working on a modpack for myself and some buddies, and I just spent a couple of hours looking through my mods and figuring out what mod could be causing an issue that I had and initially sent to the tinkers team due to the console errors referencing them.
SlimeKnights/TinkersConstruct#3116

Basically this error would make it so that anytime I melee killed a mob with sword or damaging tool it would not drop any loot, including the various item drops like hearts from dungeon tactics and money/drive/mana/xp orbs from Kingdom keys recoded. I didn't suspect it for a while but eventually when this mod and several others were taken out it stopped and the witches I was testing this against in single player who were no longer dropping loot due to this error dropped loot and my console didn't spam. After a few more attempts I found that this mod is the one causing the error.

Do you have any idea what could be causing this or what kind of interaction you believe it could be having? This looting event error and lack of drops would persist with everything melee related, but I found that shurikens and probably by extension other long ranged projectiles (and even some melee weapons) would either crash the game (the case of Xigbars guns from kingdom hearts and the swords from enchantment changer) if they linked back to a weapon or would work and drop loot as normal.

confirmed. I re-added all other mods i had previously and left this one out. no more looting event issues in console. Good luck finding the issue. :)