While having a two-handed weapon in hands will sometimes delete the weapon when using ladders (deer stands and such) (even though the weapon is now visible in the right hand instead of both hands, it is as I have nothing in my hands and the arms and hands are positioned and moving as an unarmed player.
It is as if it is random (possibly when the server is handling too much information at a time and the animation to drop the weapon is skipped).
Tested with AKM, Blaze and a Mosin.
Tested on a public hive server running patch 0.59.131121 Stable branch.
Population on the server was low (1-5 players)
Tested at day and night, server time.