I have a client using GA4 that is experiencing some anomalies in how GA4 is assigning Session default channel groups.

A large portion of their revenue (about 60%) is falling into the Unassigned channel group.

When applying the Session source / medium as a secondary dimension I also get (not set).

After doing some research this is the troubleshooting checklist I came up with as a starting point:

  • utm parameters
  • measurement protocol
  • verify GA4 set up
  • data streams
  • filters
  • referral exclusion list
  • GA4 config tag firing
  • audience triggers
  • Google ads related tagging issues
  • session_start event missing
  • Streaming events from other platforms to GA4
  • Cross-domain tracking
  • issues with analytics implementation

My question is two fold:

  1. has anyone else experienced something similar and what was the outcome?

  2. is there anything else anyone would recommend troubleshooting in addition to the above?

Any help would be greatly appreciated!

1 Answer 1


Your checklist is excellent.

We have experienced something similar.

Our problem was:

  • An implementation with gtag instead of gtm
  • combined with custom labels for universal analytics at both user and hit level (second on your checklist) to have proper trakcing in ua
  • combined with a custom consent tracking implementation that somehow makes the session start event not trigger on the landing page pageload (tenth on your checklist)

We got rid of the unassigned traffic by killing gtag with fire. (Thank you Google for that terrible advisory.) We hope to get rid of the false/missing session_start event by switching to cookiebot. Note that our platform is a spa, which is why we needed all the custom metrics junk to correct UA.

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