On SRX5k, you may find sometimes CB alarms like the one below:

root@srx> show chassis alarms no-forwarding

2 alarms currently active

Alarm time       Class Description

2023-03-21 07:20:50 UTC Minor CB 0 Fabric Chip 1 Not Online

2023-03-21 07:20:43 UTC Minor CB 0 Fabric Chip 0 Not Online

if the below error is reported along with the CB alarm:

Oct 24 21:47:11  fpc3 HSL2: Primitive train_rx XMCHIP(0)-chan-rx-16 failed to complete word alignment. 

Oct 24 21:47:11  fpc3 cmtfpc_fm_hsl2_train_rx_msg_handler: failed pfe 0, plane 0 , phy_plane 2 rx channel 16

You may ask to swap the FPC with another FPC and see if the same error follow the slot number after reboot or temporary remove it and check the alarm status after reboot.

The FPC in question requires RMA most of the time.