So it took me reverting to an older build which worked and building up again to figure this out:
There’s a piece of geometry I’m using for testing which is in front of the player when they spawn in. The error only flags up if the raycast hits a piece of geometry. Converted it to a static mesh and the errors go away!
So I’m not sure exactly why still but geometry doesn’t do well with tags and/or linetraces I guess.