It's a known bug (I mean feature) in the Windows calculator. The calculator tries to be "smart" and add the Unicode characters:

E280AC Pop directional formatting
E280AD Left-to-right override

So it ends up looking like this in the cax file:


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Not sure what Microsoft was thinking when they chose to make that brain-dead decision.
Lots of complaints online... Google for: windows calculator clipboard error

Regards
Paul