I checked the readings from the flir with a ultra small thermocouple made from GG-KI-36-SLE and an AD595 / 9V battery
It is a bit difficult to get a 0.3 mm thermocouple attached but I managed.
The readings from the thermocouple attached to the resistor with Kapton tape was around 120C. Was not perfectly connected. Still way too high.
Few uncertainties remain. Emissivity used in the flir was 0.95. Are the components being measured correctly?
Thermocouple was not calibrated above 100C.
Anyway, I remain confident that the resistors and diode are being overstressed.
And for those who think it is ok, it would be nice if you power your Siglent on for at least 3 months, 24/7. And then report back here what happened. Would be nice if you could take pictures.
Does anyone dare?