SITREP:
- Self-hosted LND/LNBits: failed (I'll check the logs when I get home)
- Coinos in DDG browser: failed, crashed browser
- Coinos in Vanadium: failed, unable to route (with a 66 sat fee)
- Coinos in Vanadium with a 166 sat fee: success!

The register didn't lose my order, despite the extended amount of time it took me to pay (probably 4-5 minutes). So good job there, kiosk dev team.
I'd still be hard pressed to recommend a non -custodial lightning wallet at this point. I hope to change that by continuing to post my experience and help test with real world transactions.