My issue was /researchresearch
was not using page-research.phppage-research.php
but instead using archive.phparchive.php
I resolved it not by the "Static Pages and Custom Post Types cannot have the same slug" solution, but on the dashboard in Settings -> Permalinks it.
It was on "Day and name" and I changed it to "Numeric" and the research page loaded from page-research.php!page-research.php