Comment 92 for bug 1573959

For me updating to the 4.8 kernel fixed this issue but gave me another suspend related issue which I reported here:
https://bugs.launchpad.net/ubuntu/+source/linux-hwe/+bug/1699436

I eventually gave up on it and switched to using hibernate.
sudo pm-hibernate
or
sudo pm-suspend-hybrid

If these work for you there are instructions online for removing suspend from the GUI menu and adding hibernate.