Upon startup, top email displayed is the 2nd email present in the inbox. If 1st email is one at top when leaving TB, next startup will show the 2nd email on top. You can then scroll up and see the top one. Likewise, if a new email come in, it also shows the one below that as the top one and must scroll up to see it. No emails are lost, just a display thing. Don't recall which version this started, but it didn't use to do this.

TB 115.11.0 (64-bit) Supernova, Windows 10 22h2