We recently upgraded our azure analysis services data model to the 1500 compatability level to leverage calculation groups. The issue that followed was pretty specific so I will try to explain it well, these are the conditions it occurs under:
1. Power BI Connected to azure analysis services 1500 compatability level
2. Measure within AAS Model uses the USERELATIONSHIP() function
3. Power BI report has a new measure definition saved with the report that references the measure in the AAS model that uses USERELATIONSHIP()
When these conditions are met, our measures are showing completely incorrect data. It took down quite a few reports when we upgraded yesterday and now we are scrambling to fix it. No changes were made to the model schema besides adding a calculation group and updating the model to 1500 compatability and now many reports are no longer reporting accurate information.