Manually failing over a few minutes after an HA passive device comes back up from reboot always results in a path monitoring failure on the new HA active device

• HA passive device has been rebooted.
• Manually failing over a few minutes after an HA passive device comes back up always results in a path monitoring failure on the new HA active device. 
• The issue is normally observed during PAN-OS upgrade. 

admin@PA-460(active)> show log system direction equal backward | match "path-mo\|1/[34]: MAC Up\|state-c\|ha2-lin.*up$\|Autocom\|system-\|System"
2025/09/09 01:57:16 critical routing defaul path-mo 2  Path monitoring for static route destination 0.0.0.0/0 with next hop XX.XX.XXX.YY recovered. Route restored.
2025/09/09 01:57:16 critical routing defaul path-mo 2  Path monitoring for static route destination 0.0.0.0/0 with next hop XX.XX.XXX.XX recovered. Route restored.
2025/09/09 01:56:40 info     port    ethern link-ch 0  Port ethernet1/4: MAC Up
2025/09/09 01:56:39 info     port    ethern link-ch 0  Port ethernet1/3: MAC Up
2025/09/09 01:56:39 critical routing defaul path-mo 2  Path monitoring failed for static route destination 0.0.0.0/0 with next hop XX.XX.XXX.YY. Route removed. <---
2025/09/09 01:56:39 critical routing defaul path-mo 2  Path monitoring failed for static route destination 0.0.0.0/0 with next hop XX.XX.XXX.XX. Route removed. <---
2025/09/09 01:56:35 high     ha             state-c 0  HA Group 55: Moved from state Passive to state Active <---
2025/09/09 01:54:50 info     ha             state-c 0  HA Group 55: Moved from state Initial to state Passive <---
2025/09/09 01:54:43 info     ha             ha2-lin 0  HA2-Backup peer link up
2025/09/09 01:54:43 info     ha             ha2-lin 0  HA2 peer link up
2025/09/09 01:54:27 info     ha             ha2-lin 0  HA2-Backup link up
2025/09/09 01:54:21 info     ha             ha2-lin 0  HA2 link up
2025/09/09 01:54:10 info     general        general 0  Autocommit job succeeded
2025/09/09 01:54:04 high     general        system- 1  The system is starting up.
2025/09/09 01:49:27 info     ha             state-c 0  HA Group 55: Moved from state Passive to state Suspended
2025/09/09 01:49:27 high     general        system- 1  The system is shutting down due to CLI Initiated.
2025/09/09 01:49:27 high     general        general 0  System restart requested by admin <---

• PA-Series Next-Generation Firewalls
• PAN-OS 10.2 branch

1. Connect HA2 port of an HA Active and a Passive devices directly.
2. Enable "HA2 Keep-alive" option under GUI: Device > High Availability > HA Communications > Data Links > HA2

Note:
The "HA2 Keep-alive" configuration is not synchronized between an HA Active and a Passive devices, so enable the option and commit on each device.