The earliest recollection of this bug is traced back to PAN-OS 9.1.6 - July 29, 2024.
This bug is fixed in PAN-OS versions 9.1.6.
Fixed an issue where traffic didn't hit the intended Security policy if SSL forward proxy was enabled and service was set to application-default .
For more information:
https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-release-notes/pan-os-9-1-addressed-issues/pan-os-9-1-6-addressed-issues