I have BigDebuffs enabled for all unit frames on Manual anchor. In certain cases when a unit has an icon active, and that unit stops existing, the icon will incorrectly remain active. Usually happens when changing zones, leaving instances/arenas/etc, people joining/leaving party.

Some examples should make it clearer:

• If I leave the arena while an arena opponent has a cooldown up, the BigDebuffs icon on the arena frame will persist forever (until I join another arena or reload ui)
• If my party member has a cooldown up when the party is disbanded, the BigDebuffs icon on the party frame will persist forever (until I join another party)
• If I'm targeting someone with a cooldown up and I leave the zone, the BigDebuffs icon will persist (until I target something again)