@Gwen-Dragon thanks for taking time to reply. No i havent been on Win7 for a long time. My current machine is always as up-to date as it can be. Currently Win10 Pro, version 21H1. I notice it tends to be the trend to list the spec in the signature, sorry for not doing that. If it has any bearing mine is Ryzen7 2700X 8 core / 64GB RAM.
Furthermore, i notice previous posters saying about size of a particular download, i dont think that makes any difference, as i have seem small files such as just 9MB from GitHub show this strange phenomenon.
Im sort of convinced its something to do with the Vivaldi Cookie Crumbler update, although there have been a couple of minor Vivaldi iterations since then. I will experiment with my work laptop which is a truly awful spec and still has Win8. I have not enabled the Cookie Crumbler thing on that one. But i hardly ever need to download anything on it, instead favouring my beefy desktop machine. Ill see what happens.