Might have found something,

I process Updates in analysis Services but I changed the problem dimension to Process FULL and it failed and it looks like there is Some issues.... E.g.

Attribute relationship [School Name] -> [School DFEE] is not valid because it results in a many-to-many relationship.

so At least I have somethint actually sort out now.

Does this mean that its best to always process FULL because the Update is hit and miss?