Gain an Endurance Charge every 12 seconds mod inconsistent behavior. bugged

With the searing exarch body armour mod "Gain an endurance charge every 12 seconds" and 20% increased endurance charge duration (i.e. duration of charges is identical to refresh time) you will sometimes stack charges to 2 and sometimes ends and thus starts a new stack of charges.

Seems to be because of server tick 'randomness'. This behavior used to ALWAYS stack. Regardless it should always do one or the other (always stack or always end duration) not have undefined behavior.

Edit: Currently my character OptiVshatter demonstrates this behavior

bump. this bug has existed for at least 10 months, previously reported here:

https://www.pathofexile.com/forum/view-thread/3247839