Unknown traffic source/workload when enabling external auth

Firstly, apologies if this is in the wrong place, I wasn’t sure what this falls under

I’ve followed the istio tutorial on enabling external auth and implemented my own auth service. It’s all working perfectly.
However, in Kiali I’m seeing an ‘unknown’ traffic source in the graph along with an unknown workload and unknown namespace.

I can’t fathom why. Has anyone seen this before? Is it normal? What would be the best way to debug?