ESRI,
I am also experiencing a similar problem with selections of related records in related tables in SDE/SQL Server since upgrading to ArcMap 10.6.1 or 10.7.0 from 10.6.0. Our schema involves a point feature class related to a table (1-M) using an integer value ('tree number') for the relationship.
Steps
(1) Open Attribute table for Hazard Tree points and run select by attributes (query Actions='Yes'). This selects 5968 Tree points.
(2) Within the attribute table, use the button to transverse to the related table called Survey. The software takes a minute to think then produces a small set of results (approximately ~2400) but not as a selected set and not colored blue and the tab for selected records is empty. In ArcMap 10.6.0, 6840 records are correctly returned. I am concerned that the "fix" to the bug described by Don Patterson above in 10.6.1 may have inadvertently introduced another bug.
Additional Information (ArcPRO select by attributes and selected records does work)