Apache Bad Request for ASA Syslog filtering by program

Hello,

While trying to filter Syslog for ASAs by program, I receive a 400 Bad Request from Apache.

I was able to figure out that it's due to somehow broken quoting of "%" sign used in the ASA's Syslog program and the issue may be related to Observium's URL Rewrite scheme.

Screens of the error are in the attachment. If you need any more info, please ask.