When mac-persistence-timer expires after the master VC member is down/halted, the MAC address of the IRB interface will be switched to a new one according to the new FPC, but it will not be programmed in the hardware, which might result in all traffic related to IRB interface be dropped. 

This issue might be seen if the following conditions are met:

• On EX2300/EX3400/EX4400/EX4300/EX4300MP/EX4600/QFX5100 virtual chassis platforms     
• An IRB interface is configured with members across master and backup VC
• The mac-persistence-timer expired after the master VC member was down/halted

root@device> show interfaces irb
Physical interface: irb, Enabled, Physical link is Up
  Interface index: 100, SNMP ifIndex: 200
  Type: Ethernet, Link-level type: Ethernet, MTU: 1514
  Device flags: Present Running
  Interface flags: SNMP-Traps
  Link type      : Full-Duplex
  Link flags     : None
  Current address: xx:xx:xx:xx:11:22, Hardware address: xx:xx:xx:xx:33:44 << The current MAC address and hardware MAC address are inconsistent

To recover the device from the issue is to reboot the VC:
root@switch> request system reboot all-member

To avoid the issue from re-appearing in future you can disable mac-persistence-timer in advance:
set virtual-chassis mac-persistence-timer disable
 

Refer to the below-mentioned PRs for the fix of this issue.

https://prsearch.juniper.net/PR1484440 >> [EX4600/QFX5100]
https://prsearch.juniper.net/PR1556124 >> [EX4300]
https://prsearch.juniper.net/PR1557229 >> [EX3400/EX4400/EX4300MP]
https://prsearch.juniper.net/PR1636422 >> [EX2300]

In addition, you need additional fix for the latest.
​​​​​​​https://prsearch.juniper.net/problemreport/PR1648310

09-09-2024: Added PR1648310.
05-09-2024: Added internal comment as the same issue is seen with fixed version on EX2300VC.
22-08-2023: First Draft - [EX3400/EX4400/EX4300MP]
18-02-2023: Added remaining platforms - [QFX5K/EX46], [EX4300] & [EX2300]