The SRX5400 device may boot from the alternate media, which results into "Minor Host 0 Boot from alternate media alarm' Minor alarm. In this case, the device was running on the OAM volume since it failed to boot from Junos volume.
 

root@SRX5400> show chassis alarms
node0:
--------------------------------------------------------------------------
1 alarms currently active
Alarm time Class Description
2024-05-06 05:04:32 PDT Minor Host 0 Boot from alternate media

node1:
--------------------------------------------------------------------------
No alarms currently active

The device boots runs on the OAM volume, so following output is observed if we run snapshot recovery command.

root@SRX5400> request system snapshot recovery
node0:
--------------------------------------------------------------------------
ERROR: You are currently running Junos on the OAM volume
ERROR: A recovery snapshot is not possible
node1:
--------------------------------------------------------------------------
Creating image ...
Compressing image ...
Image size is 2120MB
Recovery snapshot created successfully

Look for the recovery snapshots available on the node, if it's available, proceed to reboot that node. The device will boot up from the Junos volume if the file system is intact and not corrupted. Run the command below to check for the snapshots available on the nodes.

root@SRX5400> show system snapshot 

node0:
--------------------------------------------------------------------------
Non-recovery snapshots:
Snapshot snap.20230308.051642:
Location: /packages/sets/snap.20230308.051642 <<< Non-Recovery snapshot available on the node
Creation date: Mar 8 05:16:48 2023
Junos version: 21.2R3-S3.5

Total non-recovery snapshots: 1

Recovery Snapshots:
Snapshots available on the OAM volume:
recovery.ufs
Date created: Wed Mar 8 05:19:09 PST 2023
Junos version: 21.2R3-S3.5

Total recovery snapshots: 1

The the above method does not resolve the issue contact JTAC for further assistance.