A user (Dennis Rieger) discovered that when running high loads around 8.5A over a number of hours, radiant heat from the nearby lamp and current sense resistor can cause the MOSFET driver to overheat, output poor gate drive and then that can take out the MOSFET.

While that hasn't happened to me, the lamps I use may have better silvering on them which sidesteps the problem.

I did a board redesign and accommodated space for a small heatsink on the IRF3205 NFET (improved from the Z44) and made room for aluminum (soda can) material or brass (craft) sheet to be used as radiant heat deflectors.