Dynamics 365 is a temperamental mistress – everything is fine until it is not. Export to Excel has been working for a customer like a clockwork but then one day, without any warning, attempts to export this view:

started to generate this error:

(Clicking Show technical details would give some useless generic error with the invitation to contact system administrator a.k.a me)

Let me show the first screen again:

See?

While column names must be unique in Dynamics 365, nothing prevents customizer from creating two fields with the same Display Name. Everything seems to work fine but export to Excel dislikes duplicate column titles very much. Making the display name unique (per view basis at least) tamed the beast.