Hello,
monitoring fuel temps at northernly flights there is not a true °C indication, however depending on TAT the values cycle upward every 5 sec. At FL309 e.g. with TAT -22, SAT -54°C values begin at -22° upwards to -5°, at SAT -49° from -17 to -1°, and so on. Not a bug for sure, but Maybe there is a slight glitch?
Kind regards
Fritz B. Boecker