XF 2.1 Template Merging: "Template tags are not well formed"

[Anomandaris]

Using UI.X 2 and just upgraded a bunch of plugins, ran into an issue I've never seen before when merging templates:

Template tags are not well formed. Tag contentcheck was found when expecting if. - Template name: public:thread_list_macros

The code starting at line 82:

</li>
</xf:if>
</xf:if>
</xf:contentcheck>
</ul>
</xf:if>

Any advice on how to fix?