Power BI stores support/temp/cache files locally under the user’s Local profile. I am a light user of Power BI and I have a relatively large amount of junk in the directory shown below. For users of the hosted service and desktop IDE, the “Power BI Desktop” folder just above the “SSRS” one has the same folder structure. The \TempSaves folder is also where those auto-recovery files end up which you occasionally see messages about in the desktop when opening a report.
If you clean out the cache, trace, and temp save files occasionally, it should address your issue.
John