Hello Thomas,
You can also check if you have this same file revision in your Wazuh manager by accessing it at the following path:
/var/ossec/ruleset/decoders/0100-fortigate_decoders.xml
If you wish you can share with me a log line and I will check its decoding in my Wazuh manager.
Let me know if this information is useful to you!
Regards.