I also had an issue in coop and solo where I could pick up inoculator charges but my counter would not refill. I managed to resolve this issue by changing the inoculator loadout. I was using a +400% damage boost but changed it to +200% which allowed me to pick up the charges from the crates again. 

I regularly play with 2 friends and we have all had exactly the same issues since the last patch  

My psn id is the same as my username here. 

Hi,

It happened to me as well BUT only when one of the ability of the innoculator mentioned that the character will get +20% (for example) chances to get extra charge from medical supply chests.

On a map I found several medical supply chests and only the last one gave me an extra charge (I mean actually adding one charge to the innoculator charge count display).

When I used another innoculator not having this ability, I could recharge my innoculator normally.