I've tried to reproduce the issue in this Dojo example but with no success. Can you check the Dojo and let me know if it demonstrates the correct behavior that you expect to have from the Grid's 'export to Excel' functionality?
If the issue is not reproducible in the linked example, can you edit the provided Dojo in a way the error after the 'Excel export' will appear? Send me the edited project back and I will further investigate the case.
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