I have SplunkAdmins app installed and received alerts showing me that my Universal Forwarder on a series of Windows servers are having their "1 - Parsing Queue" backup pretty often. I don't have much installed there except Splunk_TA_windows. Point me to any good docs on troubleshooting Parsing Queue backups on the UF itself?
Tracked down the problem on the UF's parsing queue to basically a limits.conf setting on KB per second. Needed closer to 1 meg per second from these hosts and had it set to 512. Once I tuned that the queue alerts went away.
The UF does not have a parsing queue. The error message you cite is part of the "Indexer Queues May Have Issues" alert so I suspect your configuration has mixed up indexer and UF host names. Check the setting for the indexerhosts macro.