Issue: Occasionally, on startup, TAF would present a factory settings restored message. This wouldnt happen everytime, but often enough to be annoying.
Solution: Easy things first - removed battery holder, soldered in new external battery holder with new batteries, issue still persistent. Checked for 4,5v at RAM chip U8 at pin 26,27,28 - measured ok. Changed RAM chip at U8 with known good 6264 - issue still present. Checked for 4,5v again - it was reading 0,xx suddenly. Tapping the diode with the finger at position D2 restored the 4,5v sometimes, sometimes not.
Seems that D2 had some whacky internal fault which causes it to react on vibration, and tapping it caused it to fail at times. Replaced D2, issue resolved.