Date table relationship not working perfectly

Hi,

I have a SQL data table I'm pulling from Navision 2015.  I then have it linked to a calendar table (I started with one that I created myself in excel, then also tried moving to one created in power BI).

Everything looked like it was working fine.  I can filter by months, and years etc.  Then I noticed there is a small number of rows that don't relate properly to the calendar table.

For examle, If I was to filter on July 2017,  I would get all the sales for July 2017, but then also get some transactions with a date of 8/1/17, 9/1/17 and 11/1/17.   It seems that the extra dates are aways on the first of some other month.  Also, not all months have this problem.

If I go into the table detail (where I added some extra relationship columns to pull over month and year from the calendar table).  I can clearly see 8/1/17 as going to July 2017

But if I go to the calendar table, 8/1/17 is clearly going to August 2017 as it should be.

If I go into edit query, both sets of dates are set as date.  I've also tried setting both as date time.  Still same problem.

Any ideas?