Document Library Sync (Using OneDrive) Showing Old Versions of Documents in File Explorer?

I have a colleague who has his SharePoint document library synched using OneDrive, so that he can access his files using file explorer as opposed to his browser.

We've come across an issue today where when viewing a particular file in file explorer, it's showing as last modified yesterday (an older version). However, if the user goes to SharePoint via their browser, they can see the same document but on the latest version, last updated 5 minutes ago.

As far as I am aware the user has been consistently connected to the Internet with no errors in OneDrive. Does anybody know any reason as to why OneDrive Sync is showing the user old document versions in file explorer? Is there a delay between syncs? Does it not stay updated in real-time?

Thanks!