The router has 1 PPS signal failure (probably due to a transient hardware failure) and as a result the router has big phase offset:

user@router> show ptp lock-status detail
Lock Status:

Lock State : 5 (PHASE ALIGNED)
Phase offset : -0.000131589 sec.   <<<<<<<<<
State since : 2024-04-13 06:59:01 CEST (01:16:01 ago)

Selected Master Details:
Upstream Master address : 84:c8:07:ff:fa:10:d2:01
Slave interface : xe-4/0/0:1.0
1pps reference state : Sync failed <<<<<<<<<  

Nethertheless, the router send CC6 (Clock Class) in PTP messages to the downstream PTP peers. As a result, the downstream PTP peer can choose the affected router and get synced to the bad PTP synchronization source even though an alternative synchronization source is available.

The issue has been fixed, the fixed releases can be obtained by contacting JTAC. The fix is to worsen the CC in case the 1 PPS signal failure.