Originally Posted by Sem
Either your timing is wrong and you make a different move, or two moves/options are combined to one key. I don't sheath my weapon with LMB nor RMB, so how can I sheath my weapon with a combination of LMB and RMB.

Aim at downed foe so name is highlighted, hold RMB, click left. No changed keys/mouse settings from default. I tried it with two different mice even and get the same results.