Hmm. I haven't witnessed this. Are you able to create a simple repro with dummy data and share the cube backup and the PivotTable? I'd be happy to look at this.
Is it Multidimensional? Tabular? What exact version number when you connect SSMS Object Explorer shows on the SSAS server node?
Is it Multidimensional? Tabular? What exact version number when you connect SSMS Object Explorer shows on the SSAS server node?