Lose TRACK_PHASE due to sloppy Gandmaster clock quality
Loss of TRACK_PHASE is observed when HPSEC in timeReceiver mode, connected to a WR switch Grandmaster that is synchronized to a 10 MHz and PPS generated by a Keysight 33600A waveform generator.
The HPSEC gain schedule results in a PLL bandwidth in the order of 0.5 - 1 Hz:
Gain schedule stage: 0, Kp: -5500, ki: -30, shift: 12
Gain schedule stage: 1, Kp: -3000, ki: -5, shift: 16
The quality of the Keysight waveform generator is worse than the Morion MV336 OCXO which results in random, infrequent (once in a few hours) loss of TRACK_PHASE due to the fact that:
see ppsi/proto-ext-whiterabbit/wr-servo.c
abs(ts_offset_picos) > 2 * WR_SERVO_OFFSET_STABILITY_THRESHOLD
This phenomena disappears when the PLL loop bandwidth in the order of 20 Hz:
Gain schedule stage: 0, Kp: -5500, ki: -30, shift: 12
Gain schedule stage: 1, Kp: -5500, ki: -30, shift: 12
Conclusion: The loss of TRACK_PHASE is not a bug but merely the result of a poor Grandmaster in combination with a high quality timeReceiver.