well, that fixed itself.
The Content > Forums view was actually outdated, somehow.
What happened is that we have a new forum created weekly (it's a football site, so we have a new forum for each game week of the season). Last week's forum gets renamed, the one prior to that one gets moved to an Archive category, and the current game week forum is created. Well, one of my mods did all of this, and the new game week's forum was the one showing issues, and it was missing completely from Control Panel. When I viewed Control Panel, I was still seeing last week's and the prior week's forums. When I edited and re-saved last week's forum, it updated & fixed everything. The Content > Forum view is now correct and the breadcrumbs on the actual forum page are correct now as well.