For a long time now every time OneDrive updates (read installs a new version - in the background - by itself - triggered from a scheduled task or something) it opens its container folder in a new dopus lister.
I suspect the normal explorer is somehow ignoring it but when dopus is set as default handler this happens. It happens without any user interaction at all and also defocuses the active window in some cases which is unacceptable.
A solution would be for dopus to just ignore the root onedrive folder when passed as an only argument via the command-line.
It's been doing this for a very long time but it's become a nuisance and has to go.