As you can see on my image, my inventory is quite full. I wanted to equip dagger B (I had two). I already had equiped one of my daggers, dagger A, and a quiver was still on my offhand, I made some room in my inventory to store the quiver, right clicked on my dagger B to equip it and it disappeared.
(log file is attached)
“Item could not be successfully equipped, possible mismatch from precheck and item add attempt” (all way down, last lines)
https://imgur.com/8d43b1k
Player.log (26.7 KB)