What was the device? Somebody experiencing the same problem might appreciate the tip.

It's the LTS5 from Dragino, a LoRa touchscreen: https://docs.dragino.com/docs/LoRaWAN-End-Node/lora-modules-.... And for the record, I'm extremely happy with all their other products, which are all open-firmware, open-hardware, etc. and excellent quality. Plus they're super responsive. It's just this particular product which has this weird issue.

There's all sorts of cheap devices like that out there that merely have a Type C-shaped receptacle that doesn't actually implement Type C because they couldn't bother to place two resistors on the board.