When I use the "Search" (Ctrl+K) option from the sidebar, as soon as it starts to search (so after I type at least three letters and pause) the search box disappears, as does the sidebar and the top bar and basically the entire World Anvil UI frame, leaving only the main page I was looking at. I can only get them back by refreshing. I had someone else test and this happened to them, too, so it's not just me.
Confirmed on Firefox 124 with clear cache and addons disabled.
This should now be resolved. The issue was indirectly connected to the icon loading issue (due to a FontAwesome outage earlier today).