It is when things don't work as expected that it's really hard to find help. We had this issue happen a couple of weeks ago where we were trying to connect from one of our clusters to an Elasticache instance. We could connect to it from a namespace with istio sidecars disabled but not from a namespace with it enabled. We could also connect to it from a namespace in a different cluster which did have istio enabled. It took nearly a week to figure that out because there is so little prior art (in terms of stackoverflow questions, github issues etc). This comes with the territory of using something relatively new I suppose.