Merge problems - incorrect expand

I've recently encounterd a similar problem.  Through my own testing, the error (where values are switched) appears to be triggered when a merge is expanded AFTER a grouping event has been conducted in Power Query. 

I went so far as to limit my data fields to just 1 row and found the error still occurring.  While the error is observed in the merge/expand step - the symptom appears to be triggered when merges are placed after a grouping event.  

(The grouping event is not pictured - and additional transformations were conducted between the grouping event and this pictured merge)  The errors impacted a subset of rows (less than 10%).  Below I've singled out one of the changed rows to try and problem solve what might be causing it. 

Merging 1 Row to 1 Row

Pay attention to the values in "First Date"

I can reproduce this readily and it seems like a pretty big issue.  I've been using Power BI since 2015.