Hello and welcome,
im quite new to the platform myself but, could you explain the procedure you are using to upload the excel file?
So far i have uploaded a few and got a few errors but none like that, since to my knowledge if you are uploading it into the entities there are no "assumed" types.

I used the loop through as excel tutorial as my base and made an import page.  When I click on the import excel, I get the error.  I've had no trouble with the other import I did.  I am just importing an instructor name, date, start time, and end time.  The only thing I can think might be causing an issue is that the instructor name is an identifier for another table.