displaying Tumblr in Firefox

Tumblr seems to freeze Firefox fairly often on my computer, e.g. I scroll down my dashboard and then suddenly the page (and all of Firefox actually, like I can't switch tabs) becomes unresponsive for a little while before scrolling resumes. At first I thought it might be some unfortunate side effect of XKit or an XKit extension, because the filtering that applies to my dashboard (like removing the sponsored stuff, and blocking some tags), and that used to slow things down on my old laptop sometimes, but this effect also happens sometimes when I have just a single Tumblr post open and scroll down that.

Do others have this problem? It is starting to really annoy me. It never happens on any other website besides Tumblr.