Under the hood
Useful1 Signal2
Session registration can write its process-id file through the newer store when one is available.
What's wrong with this entry?
Anonymous. No account, no email.
What
When a storage handle is supplied, session registration writes its process-id file through that store and throws on failure; without one it falls back to writing the file directly to disk as before.
Evidence
v5 pid-file write failed
Strings lifted out of the shipped bundle, so the claim above can be checked against them.