PHP 7 and login/registred user don't work

[PierreRel]

Hi,
After I upgrade my dev environment to PHP 7.0.8 I can no longer login a user on the frontend running Meet Gavern template. Everything works fine on backend and site is working as expected on frontend with Meet Gavern template. When the user logs in I get an Error 0, Page does not exist. Looking at the backend I can see that the user have been logged in. If I force the user to log out (from backend) the user can browse the public site again but as soon as user logs in the error page appears.

If I change to another template everything seems to work fine.

I have not been able to find the solution, so I reinstalled my dev environment with PHP 5.5.37 and restored site from backup and now everything works as expected.

My conclusion is that Meet Gavern and PHP7 has some kind of missmatch, but I'm not the star to figure out what is causing the real error. I tried the usual stuff to turn on all error reporting but could not see any strange things. Best guess right now is some conflicting js handling, might be associated with login in modal view...

Kind Regards
Pierre