I found this comment on what happened by dani-garcia, one of the main devs:

The short version is that around 8-ish years ago, Bitwarden changed the way the vault items were structured, and Vaultwarden added some backwards compatibility fields to ensure both old and new versions of the clients worked.

These backwards compatibility fields were supposed to be a temporary measure, but for at least the next three years the clients still required them, until we eventually forgot to keep track of them. At some point between 2021 and today, the clients stopped requiring these backwards compatibility fields, but Vaultwarden was still sending them.

This wasn’t a problem until Bitwarden decided to use the backwards compatibility fields in a completely different way, which caused the clients to crash.

Found here: https://github.com/dani-garcia/vaultwarden/discussions/7473

Would this make them useful to side load your own firmware to them? This “exploit” could make these into a hobbyist’s dream