When deploying a fence kit:
(left click deploy, select a valid location on the ground [ghost image gets darker], hold left click, circle fills)

If the process is interrupted during the 'hold left click' phase such that fence kit deployment stops and the circle vanishes, there is a chance that the player hand slot becomes bugged and the fence kit disappears. Actions involving the player's hands will not function after this, and the player's hand state may desynchronise with other players in the vicinity (e.g. one player sees me carrying a log, I see my hands as empty).

The fix is to re-log into the server, whereupon the previously-vanished fence kit will be held in the player's hands. Normal functionality will be restored.