They can cause all kinds of conflicts and errors that may also affect the gallery and make it time out.
Mods still have many many issues since the patch and it's been really tough to sort through anything.
For ANY report in the bug forum, mods will always need to be removed so if an issue pops up, all bases need to be covered first, especially since it was working perfectly fine for me when then this was first reported. Gallery outages usually affect everyone unless they're local to certain regions.
This one seems to have been that's I just gotten gradually worse now and as you can see by the status tag, this is since under investigation.