Import users via CSV import hangs

I'm trying to import users into a Dev env via CSV, and the UI is hanging.

File looks like

email,id,email_verified,first_name,last_name,hashing_method,hashed_password
user.name@domain.com,ANid,TRUE,Name,LNameD,bcrypt,PASSWORD

email,id,email_verified,first_name,last_name,hashing_method,hashed_password
user.name@domain.com,ANid,TRUE,Name,LNameD,bcrypt,PASSWORD

email,id,email_verified,first_name,last_name,hashing_method,hashed_password
user.name@domain.com,ANid,TRUE,Name,LNameD,bcrypt,PASSWORD

email,id,email_verified,first_name,last_name,hashing_method,hashed_password
user.name@domain.com,ANid,TRUE,Name,LNameD,bcrypt,PASSWORD

No error messages in the console either.
Any ideas?