Power Charge on Crit Martial Artist BUG

Gloves has 14% chance for arcane surge and when i put into way of stone fist Martial Artist, the roll for power charge on crit STAYS AT MIN ROLL of 5% (5-10%)
I have DIVINED it 5 times to test and no matter what the value of Arcane surge chance is, the value for power charge chance STAYS AT 5. Is it a bug?