The earliest recollection of this bug is traced back to PAN-OS 8.1.17 - January 09, 2024.
This bug is fixed in PAN-OS versions 9.1.5, 8.1.17.
Fixed an issue where templates on the secondary Panorama appliance were out of sync with the primary Panorama appliance due to an empty content-preview node.
For more information:
https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-release-notes/pan-os-8-1-addressed-issues/pan-os-8-1-17-addressed-issues
https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-release-notes/pan-os-9-1-addressed-issues/pan-os-9-1-5-addressed-issues