Frequent dropouts with external HRM

Received my Epix 2 recently and have gone on a few runs to date. Each time the connector to the external HRM has been extremely shaky, with the HR reading "--" and frequent pop-ups of "external monitor connected" while running. The monitor is fully charged, and I have never previously experienced similar dropouts over many months of usage.

No new clothes, no other variables (that I can think of) other than the watch. I've included HR from my last run with my previous watch for reference, this has two "drops" but which were in fact me shopping to check my map.

Is this a known epix 2 issue?