Session: Error while trying to free lock for ci_session

I have the same issue.
Our site is hosted on AWS and we have ELB with 5 servers behind.
Yesterday we upgraded CI on 3.0.6 version.
We are using memcached for handling sessions.
In php.ini session handler is setup for memcached .
When I try to use CI with memcached site is loading forever.
But when I setup CI for using files the site is loading normally but have some weird issues.
For example on one page is fine but when I click on the other I have been logout or even use some previous users which I was logged in.
What should I do to make this work as it is supposed to work.
Thanks