I believe various capacitors were tried before Oztules went to the zener to cancel the high voltage trip entirely.
Interesting thought with the extra diode. I don't think it is temp drift of the zener that is the issue, tho. Temp changes to the fets as measured by the sensor on the heatsink affects the high voltage trip setpoint (it shouldn't, but does) I use external fan control circuit, so I unplug the heat sink sensor, which eliminates that variable. Using the zener eliminates any concern of temp drift anyway
welshman, thanks for the pics. They seem to have just moved R14 to the underside, which should mean putting the zener in the old R14 position should work for the folks with the newer boards (and easier than piggybacking). I wonder if the smd resistor is still a 10 meg?
For the record, I've been using a 5 meg resistor for r14 without adding the zener and with the temp sensor unplugged for several months now without experiencing even 1 trip. (Independent fan control is highly recommended before running with original sensor unplugged)