Challenge in connecting with SSAS cube-- Getting failed again and again

Dear members,

we have developed a Power BI solution which is connected with SSAS , now it's getting failed again and again, below is description of problem statment.

• The source database is 1.4TB in size;
• Team have built a Tabular Model in SSAS (on a server with 512GB RAM) which has compressed this to around 200GB;  
• PowerBI sits on a separate server with 128GB of RAM and has a live connection to the Tabular Model;
• PowerBI file consists of 15 pages (1 overview page, 14 drillthrough/filtered pages), and each page has 4-8 graphs, 3-4 display cards and 3-4 slicers;
• Calculations and measures have been created in the Tabular Model, no computing is done on the PowerBI side.
• The Task Managers on both the SSAS and the PBI server show that they are not close to maxing out the memory, however we do keep hitting 100% utilization on the CPU in the SSAS server.

Any suggestions what is Power BI specifications which we are breaching and what could be workaround of same ?