Welcome to BLF lzeppelin 
Bangood should help you with this problem. How long have you had the MF04s ?
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The driver may be ok, could be a bad switch.
The led is either bad or not seated well on the mcpcb. The leds I had the same symptoms, were bad.
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If needed Lexel probably can get you fixed up with the driver. Lexels driver compilation
PM Lexel and ask im for advice too. 
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