Gain charge every X seconds mod on body armour not working propperly

I have the mod on my body armour "Gain an Endurance Charge every 14 seconds" and in my tree also have +40% Endurance Charge Duration total, so they should generate automatically.

The issue I'm having is despite this, the charges generate up to 4 (my maximum is 5) but then instead of generating the fifth it goes down to 1 again. It's like the duration is not the same depending how many charges i currently have.

Bug report reference number: 1.790.736.309