Open node in content section first time takes very long

I noticed that opening a node in the content section takes very long (several seconds) the first time you try to open it. For example, when I log into the umbraco backoffice in the content section there is my Home node, fully closed. I click the arrow to open it to see first level subnodes (I have approx. 12 subnodes) - that takes more that 2 seconds. In Subsequent clicks everything works “normal”, unless I change the section. This is annoying.

I noticed that the effect comes only into place with Firefox. When I use Edge the node opens fast as it should.

Can anybody confirm the behaviour with firefox?

Huh, how strange, Firefox is definitely slower for me too

Left is Edge, right is Firefox:
Edge vs Firefox Umbraco Backoffice Speed Test

Edge Network tab opening a content tree:
Edge Umbraco Backoffice Network Tab

Firefox Network tab opening a content tree:
Firefox Umbraco Backoffice Network Tab

Interesting, it seems that Edge renders the tree in bit by bit as its loaded, but Firefox seems to wait until everything is loaded before rendering.

I use Edge daily so I’ve never noticed this before.

Thank you for analyzing this in detail. It’s a pity because Firefox is my standard browser and I was quite happy not beeing forced using edge - until now :-((