I'm interacting with an existing database, created in 10.2.0 & recently upgraded to 10.6.1. It contains table entries that participate in a relationship class (M:M). I've noticed that ArcMap cant reliably "show related records" for relationship classes built pre-10.5. Has anyone else experienced this issue? Has there been a fundamental change in the structure of relationship classes in the last several versions? This is not an extended relationship class.