EDIT: With some testing, I’ve changed some of the info below.
I don’t know the underlying specifics, but like other people have observed, it seems restricted to the tabs under the “Custom” game mode. I’m inclined to agree with others that it has something to do with the loading of the custom maps’ in those tabs, specifically the maps’ names.
[Above, I removed references to the issue being in the “Lobbies” tab only.]
As for the other main game modes (Campaign, Coop, Versus, Collections), since custom maps’ names don’t appear in any of them, it doesn’t seem to affect any of the other main game modes.
I know it doesn’t affect Coop because I regularly play it, even in the past few days. For the “Versus” mode, I’ll try a few of those options for experiment’s sake.
Brb.
EDIT: See my “Versus” results below.