There is a problem that does not let you upload users with a CSV file if there is a menu user profile field with spaces in the end/beginning of the menu options.

There is 'first option ' option in menu field and the same value in CSV.

username,profile_field_Dropdown

tttt,first option 

upload test.csv

When you try to add users with a CSV file you get an error 'Invalid user field: {fieldname}' even if you have the same spaces in the values of the menu field in your CSV.

If the system trims field values when you upload CSV it should also trim values when you create the list of allowed values.

It is clear that there should be no spaces at all before or after options in menu profile field. In CSV should be no extra spaces as well. CSV values get trimmed though while menu options keep spaces in their options.