Post: #2

this was caused on some previous builds when NPCs cast buff/debuff spells on players (creating spell memories linked to this NPCs), and when this NPC die, the spell memory will remain equipped on player linked to an invalid UID because the NPC doesn't exist anymore. And the worldsave will find these memories with invalid links and will remove it. Nothing to worry about, since this message is just an minor warning, not really an error

but anyway try update your SphereSvr.exe to recent nightlies, this issue got fixed some weeks ago