As discussed in the below:
Solution: Go to https://marketplace.visualstudio.com/items?itemName=ProBITools.MicrosoftAnalysisServicesModelingProjects and install the latest version, it has a fix in there to resolve this issue.
A fix for this issue has been internally implemented and is being prepared for release. We’ll update you once it becomes available for download. For now, please install latest SSAS from https://marketplace.visualstudio.com/items?itemName=ProBITools.MicrosoftAnalysisServicesModelingProjects to work around the issue. Sorry for any inconvenience.