Carl healing
Phenomenon
When you leveled up your pet C.A.R.L. then left the party, the moment you were going to kill zombies, the pet's level reset to 1 and the pet started to deal negative damage only to zombies; other entities weren't affected.
Cause
The damage multiplier broke when the pet reverted back to level 1, or a lower level than the regular one for the respective tier..
"To find the damage that should be taken, the game will check the difference between the tiers and multiply that by a constant. The difference in tiers could be negative meaning the damage is multiplied by a negative number meaning health is ADDED instead of taken away." - Apex
Message Link - Zombs Resort:#bugs
Examples
Tier 4 C.A.R.L.

Tier 4 at level 1 C.A.R.L. dealing -240 damage.
Tier 5 C.A.R.L.

Tier 5 C.A.R.L. dealing -837 damage.
Changelog
WARNING
Changelog needs to be completed