Although the router is in synch with the signal quality PRC, and the configured minimum-quality is also PRC:
 

        output {
            interfaces external-0/0 {
                wander-filter-disable;
                holdover-mode-disable;
                source-mode chassis;
                minimum-quality prc;
            }
            interfaces external-1/0 {
                wander-filter-disable;
                holdover-mode-disable;
                source-mode chassis;
                minimum-quality prc;
            }
        }

the router reports 'Tx status: squelched' on the external interface of the control board.

In the output of 'show chassis synchronization extensive' the status Tx status is squelched:

{master}
user@router-re0> show chassis synchronization extensive 

Current clock status : Locked
Clock locked to : Primary
SNMP trap status : Enabled

Configured interfaces: 

Name : external-0/0 
Signal type : 2048khz 
Rx status : disabled 
Tx status : squelched 
LED color : red 

Configured outputs: 

Interface : external-0/0 
Tx status : squelched (fail minimum QL) 
Minimum QL : PRC Tx QL : SEC (PRC)
Holdover mode : disabled Wander filter : disabled 
Source mode : chassis Source Tx DNU : disabled 
Holdover data : invalid 
Current state : holdover 
State for : 1 days, 10 hrs, 03 mins, 49 secs 
State since : Mon May 6 03:03:57 2024 

Configured sources: 

Interface : et-11/0/2 
Status : n/a Index : 397 
Clock source state : n/a Priority : 2 
Configured QL : SEC ESMC QL : PRC 
Clock source type : ifd Clock Event : n/a 
Wait-to-restore : 5 min Hold-off : 1000 ms
Interface State : Up,ESMC Rx(QL PRC/SSM 0x2),ESMC TX(QL PRC/SSM 0x2)

In the customer's case the SynchE client, connected to the external interface, reported issues with SynchE synchronisation.

The issue fixed. The fixed releases can be checked by contacting JTAC.

The workaround for the issue is to decrease the acceptible priority from PRC to SEC:

router@user-re0# show | compare 
[edit chassis synchronization output interfaces external-0/0]
- minimum-quality prc;
+ minimum-quality sec;
[edit chassis synchronization output interfaces external-1/0]
- minimum-quality prc;
+ minimum-quality sec;