Saved report layouts reverting back to default view

Hi,

I would like to know what can cause a saved (pre-existing) A-OLAP report to lose its customized layout and revert back to the default view of its underlying BEx query.  Our BI A-OLAP uses BEx queries as data-sources, connecting to them via BICS. Platform version: BI 4.0.5.1

Every so often we receive user complaints that they have lost the customized layout of their saved reports.

1. What Bex query property settings, in query designer and in BW, can affect pre-existing OLAP Analysis Workspaces?

2. What changes (within an A-OLAP workspace or in BI, Bex, BW, CMC etc.,) can make an AOLAP report layout revert back to default view?

Thanks