Turns out that the 2 cannisters of rare minerals which I scooped up in my SRV (which subsequently blew up without ever getting inside a ship again) are now, somehow, in the hold of my Cutter
I put in a bug report about this a few days after 2.3 dropped. Spent the afternoon blowing up SRV's to submit videos.
https://forums.frontier.co.uk/showthread.php/343133-SRV-cargo-bug