Excessive memory usage

I don't know whether this has been reported before or is significant but here goes. Normally, on my setup, the game uses approx 9% of my available memory (according to task manager). However, occasionally when I click on a collectible or zoom out or other fairly random operation, the memory suddenly begins to shoot upwards. 20%, 40% even as high as 80% of the 64GB I have available. When this happens, nothing in the game works and I have to close the browser window down and start from scratch. I am using Firefox by the way.

Also, I keep getting session timed out messages which I have never had before. I have no idea why. I sometines get these after 5 minutes or 5 hours - it seems quite random.