Problem opening saved docs following recent upgrade

I have recently downloaded v7.5.7.1. Now, when I open a previously saved document (in Calc or Writer) I receive a message stating ‘Document in Use’ ‘This file has been locked by another user’. I am using a home PC to which no-one else has access. I’m running Windows 10 and Firefox 118.0.2. I have to use ‘open a copy on your local system’.
Why am I getting this message?
What do I need to do to stop this happening?

Which antivirus do you use?

I use AVG Internet Security 23.9.3302 (build 23.9.8494.796).

I do not use the AVG VPN because there are so many sites that do not allow you access when you are using it.

blocked.gif

Avg and Avast are owned by same company, this link should work for AVG too, Using the Blocked & Allowed apps settings screen in Avast Antivirus | Avast

You need to add soffice.bin to the allowed list, not the exe files. You probably need to add it again for every upgrade of LO.