I have OPNsense 24.4 and after a reboot I am unable to use the Firewall: Diagnostics: Aliases Find references feature.
For several minutes after the reboot the Find references feature always returns Error while fetching matching aliases: 403
After around 10 minutes, the feature works again.
Importantly though the firewall rules using the Aliases seem to be firing correctly immediately after the reboot.
So I guess this a cosmetic issue.