I turned off all speedy loot addons and it stopped for me.
how can i block this with leatrix plus?
Uninstall any addon that “improves” loot handling and it should stop.
This worked. Thanks 
Normal auto-looting speed is barely slower than LP’s enhanced auto-looting. I can live with that
OMG…Thank you so much! Was going crazy going through all my addons to find which one was causing the issue, coming up empty handed. Perfect!