The August 2020 version of PBI Desktop 2.84.461.0 64-bit (August 2020), corrupts any PBIX that is saved using this version. Once a PBIX is saved, it cannot be opened by this version or any previous version of the PBI Desktop. It says the PBIX is corrupt. Even when I had published to the Service using the August version, where the report is working fine; if I then download the report on the Service to a PBIX, that PBIX will not be able to be opened by any version of the PBI Desktop always indicating the report is corrupt.
I had to re-install the July version of the PBI Desktop to avoid this issue.