USERELATIONSHIP function not returning correct count

Hi !

I have an issue which i will try to explain as best i can. 

I am trying to display a clustured bar chart column showing the date a ticket was "Opened" and also the date it was "Resolved" (if indeed it has been resolved). 

I have a separate  Calendar table with 2 relationships to both the "Opened" Date and the "Resolved" Date. My 2 Measures are:

1) Created= Calculate(DistinctCount(Tickets[Key]), USERELATIONSHIP(Tickets[Created}, Calendar[Date})))

2) Resolved= Calculate(DistinctCount(Tickets[Key]), USERELATIONSHIP(Tickets[Resolved}, Calendar[Date})))

The "Created" measure appears to be working fine however... the "Resolved" measure is not counting all of the Resolved tickets e.g. you can see below that for October it has counted 2 X created and 1X resolved correctly... but nothing for November.

What is slightly strange is that if i change my Axis date to be for the Year - it picks up the second Resolved ticket, but not at a monthly level e.g.

Any help is greatly appreciated!

thanks