Battery draining even after full reset

Hi there!

I have a question regarding the Galaxy A5 2016 (SM-A510F)

We fix these devices on a regular basis for a company that uses a few hundred of these.

Lately we have been encountering alot of problems with devices being drained really fast, even after a new (full original) battery swap aswell as a full factory reset.

I have to say, what i do notice is that often, these drain devices are also having WiFi issues (not being able to get WiFi to turn on, it either does not turn on at all or just keeps scanning)

Are these 2 issues maybe related more then we know/realise? Or is there any other reason the drain appears, and does anybody know if this is fixable?

Thanks in advance!