It is due to the effect of projecting this graph at this resolution.
What one would see, at a better resolution, is a pike [max-zero] each time the value of one probe is invalid (NCD: no computed data). It looks so "noisy" because the value of each probe is not sampled at the same time.
Takata.
If I understand you correctly, and read the trace correctly, when the system considers the value of the AOA to be invalid, it applies a zero value to the signal which is momentarily overridden by the periodic read of the probe, thus creating the spikes.
When the data is considered valid, the signal remains at its last value until the next read, thus only small steps, and no spikes.