We released a server-only Bugfix to restore proper defense of creatures.
Background: Because of this bug, the logic to increase def_xp of players was applied to creatures as well.
The def_level of creatures, however, is statically assigned, they don’t have any def_xp. But the broken code incremented the non existing def_xp from 0 to 1. This in turn triggered a calculation of the def_level and overwrote it with 10 (the def_level for def_xp=1).