I have experienced some oddities where joins between an SDE Feature Class (registered as versioned) and related GDB table causing attribute values to change after joining. The Feature Class has an relationship to the table and has had this for years using previous versions of ArcMap and SDE. The values that seem to change to a random number consistently are in fields that have the short integer type. However, not all values change. Both ArcMap and SDE are version 10.5.1 (SDE was recently updated) using Oracle.
The example attached shows the Polygon ID and the Number of Exams values change in the attribute table before and after the Join (on spatial ID).