In the 5.1... beta version, I noticed that the tab icons retain their 'loading' status. The swirling circles.
The page has long finished loading, but this is not reflected in the icon.
This makes it difficult to tell what page these inactive tabs are showing.
I hope it's just a visual glitch, rather than that the page is actually still working on something.
This is probably a bug that will be fixed when the official version is released.