Technical Tip: HA not Syncing - cheksum dump: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

When configuring certain interfaces as HBDEV, both the master and slave in the HA cluster experience heartbeat (HB)
packet drops, out-of-sync state, and a checksum dump showing all zeros.

Configuration Status:

FG12XXXXXXXXXXX(updated 4 seconds ago): in-sync
FG12XXXXXXXXXXX chksum dump: 55 3e 1d 50 e6 74 82 f6 da 6b 05 7e 09 60 e9 95
FG12XXXXXXXXXXX(updated 1744722639 seconds ago): out-of-sync   <----- Seems like invalid time counter.
FG12XXXXXXXXXXXX chksum dump: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <-----

Upon investigation, the root cause was identified as the (Virtual routing and forwarding) VRF configuration of the heartbeat interface being set to non-zero.

Note: 

For the affected devices, this behavior is fixed in v7.6.3.

Related article:

Technical Tip: Virtual routing and forwarding ID configuration