CSRF giving problem with ajax

Hello,

I build an application using CI3 and ajax to submit the forms, my CSRF is enabled and regenerating in each post, i use the json response to renew the CSRF values in the csrf inputs of the all forms in the page, all works fine, but some time i giving the blessed error "An error was encoutered. Your request is not allowed" right in the first submit (in this time the csrf input is write right in the html), well the funny is, after the time that the csrf token expire (for what i see) all turns work again without the csrf error, but the most strange is that not even reloading the page, cleaning all the browser and session data (using DB to store the session) it works, just sit down and say: i not will work now, wait the csrf token expire!

Disabling the csrf all turns to work (as expected) .

Well I tried some solutions but nothing works, someone please light me!

Very grateful!