Help me understand why regexp captured fields are not being forwarded.

Hello, I resisted posting here for a while but am finally at a loss to explain what I'm observing. I'm trying to send nginx access logs to graylog, and am mostly using code adapted from the nxlog ce user guide but I haven't been able to get the fields to successfully capture and arrive in graylog.

The nginx server in question logs two sorts of traffic:

AskedFebruary 4, 2020 - 6:06pm