problem after import users

Hello

i use your plugin to import some users and it seemed to be a succesfull importation of my 500 users. But after it, i find that i got a problem about cookies, in which when i log in with my admin users at backend admin it started to go slowly and im getting error 500 when i go to front end logged in.

I can’t open my frontend site loged in with any user.
Other thing is that when i tried to log out it gave me error 500 – Internal Server Error.

So i clear my cookies related to my site and ofcourse it log me out and i can see my site, but trying logged in againd keeps giving me error 500.

Have you heard about a problem like this?

thanks

https://wordpress.org/plugins/wp-ultimate-csv-importer/