Main BW app on macOS sometimes fails to launch

I have very recently moved from 1Password to BitWarden so have only just joined this forum.

I am using:

BitWarden 1.27.1 (531) (Mac App Store version)
The Firefox extension version 1.51.1 in Firefox 91.0.

My MacBook Pro (16 inch 2019) runs macOS 11.5.2.

When I boot my Mac I’m always able to launch the main BitWarden app. If I quit it and then launch it again reasonably soon it will launch without problem. If, however, I quit and do not use the app for some time it will fail to launch. By that I mean that, for example, double-clicking on the app name in the Applications folder will do nothing.

In those cases Activity Monitor reveals BitWarden still running (even though there is no discoverable BitWarden window). If I quit that process in Activity Monitor I am again able to launch BitWarden…until the next time the problem occurs.

For what it’s worth, and in case it’s relevant, I am invariably browsing in a Firefox private window (and switching to a non-private window when I need to bring to life the BitWarden extension—so that I can use the keyboard shortcut to paste login details in private windows).

I’m wondering if anyone else might have experienced this or have a possible solution.

Stephen