Suggesting I check continuity between the outer ring and the shielding?I don't think you understand what we are suggesting. That plug and attached foot and a half of cabling, unplugged from the inverter, is all that you need.
BTW I believe this is some hybrid connector Tesla has made or had custom made by amphenol. The left half is identical to an Amphenol HVPT connector however that wouldn't typically have the termination attached.
Would love to work out what the tesla connector is so I can make one continuous cable from battery to inverter vs having a junction box