After getting the body of a dead colonist out of a sarcophagus, I order a colonist to use a resurrector mech serum on that colonist, but animals assigned to hauling put the body back in the sarcophagus before my colonist can use the resurrector mech serum.
Yes, the use of the resurrector mech serum won't lock the corpse, it is just the target of an item/ability.
But noone prevent you to forbid the corpse, then noone will haul it.
As per Canute, this is simply the games storage system working as intended. Forbid the corpse or assign the sarcophagus to someone, or change the sarcophagus' storage settings.