Regen using current health

Platform, device and operation system
Android, Galaxy S20 FE

What were you expecting to happen, and what actually happened
I expect that when health regen buff is activated at start of turn health received is based on percentage of max health. Instead health received is based on percentage of current health

How often does this happen? When did it begin happening?
Any time regen buff is applied

Steps to make it happen again
Have regen buff active a lower than max health, allow regen buff to activate.