Sigh… Haikelite has good product lines, but the brand is cheap to its management as they don’t mind using fake components and caused so much trouble to customers. Mine MT03 TA had faint leaking light during off and after spending month negotiations with CS to get a new driver from Haikelite and I paid for shipping, the new driver was having same issue. Desoldered and measured both fake SIR800 to be having around 50Mohm of resistance with 0Vgs, they are not completely open.

I replaced the FET with real SIRA60 and it works fine. Also replaced the FET of another driver with BSC009 and put it into old MT03 II, it works fine too. Now these two MT03 are always in momentary mode with 5clicks, have had blasting them side by side for 1+ hour in accumulation, almost burn my hands as they are really hot.

Good thing was Haikelite forced me to learn how to use hotair gun. After watching some YouTube video, i managed to solve it to good ending.