If you haven't already done so, you might try strengthening your router password. In June 2021, Virgin emailed me to do so, presumably because it was aware of an issue with routers of a certain age.
I also found that, on my new Apple devices, I get 'weak security' messages on my iMac and iPhone. I have taken this up with Virgin Media who claim there is no such issue with VM if the router has a strong password. There is a message on this subject on the 'Networking and Wifi' forum from a Virgin Media contributor.
Good luck with this and if you find an answer, please let us know.