In my case, it turned out to be a serverside issue, which I did not expect.
Creating a new account on the official servers resolves the issue, logging back into the self-hosted instance (Vaultwarden) reintroduces it.
This is apparently not contained to Vaultwarden, some users self-hosting the official server components seem to be experiencing the same issues:
bitwarden/clients#11173, dani-garcia/vaultwarden#4983
Most of the users who posted on GitHub thread #11173 don’t actually state whether they are using the official Bitwarden server or Vaultwarden (one stated they were using Vaultwarden, and only one stated that they were using the official server, the rest don’t say). However, the Bitwarden dev working on the issue @cagonzalez was able to find a bug that would affect users of the official server, and has already implemented a fix of the issue (which should be available in the next browser extension release.