Hi - Based on the analyis and Inputs from microsoft - there has been a change in the way DAX from PowerBI generates/runs on SSAS 2016 MDX instances. This change was done because of a bug in earlier versions where it produced incorrect results.
This fix while ensures that results are accurate, in certain edge cases results in slow query performance and timeouts.
At this point there is no resolution to the issue other than
1. Try not to create reports that are very wide in Power BI.
2.Use SSRS for such reports