Try a hard refresh or clear the cache to see if that helps.
Alternatively, see if the problem replicates itself in Chrome or Firefox. We don't perform any testing to ensure compatibility with Opera, so this could be a reason why.
Did you check your system memory usage? Try creating a new windows profile and check the game from there. Make sure to log out from your main account first.
Can't blame memory usage Laptop has 6GB and this Desktop only has 2GB memory. but that will change soon. :)
Firefox is the most compatible browser, to use according to Unity themselves - https://docs.unity3d.com/Manual/webgl-browsercompatibility.html
But graphics card matters in Firefox, if using a blacklisted GPU you have to edit this and that in Flags to support it.
The same can be said about Chrome, but Edge & Opera will run straight out of box, as is. Though you can still edit the same flags to optimize their performance.