Consider something here:
SAT is impossible to measure directly @ M0.8+ and FL350. The displayed SAT is a computed number, based on measured TAT, with the ram temperature rise (a function of Mach) "backed out".
If the pitot is blocked, then the computed ram rise is in error. Depending on altitude excursions, this error could be either plus or minus direction.
Ergo, the computed SAT could be in error either direction.