Facebook OAuth Verification code verification error sometimes

I have a very strange problem with facebook user authentication. This mainly works for 90% of users, but for 10% I get the error message "Verification code verification error". They tried to log in from different browsers, and they always get the same error.

I did everything according to the book:

https://www.facebook.com/dialog/oauth?scope=email%2C+user_birthday%2C+publish_stream%2C+publish_actions%2C+user_hometown&redirect_uri=http%3A%2F%2Fapps.facebook.com%2Fbetchallenge%2F&client_id=.....

Then I take the code code from the response and send a new request:

https://graph.facebook.com/oauth/access_token?client_secret=...&redirect_uri=http%3A%2F%2Fapps.facebook.com%2Fbetchallenge%2F&code=...&client_id=212564568790055

I followed all the rules, redirect_uris are the same, they don’t have special characters like? ....

Any ideas?