Sound resets to 100% after reboot on Ubuntu 16.04

This is a bit mysterious problem.

I upgraded Ubuntu 14.04 to 16.04. Now after each reboot the sound volume resets to 100%.

It is mysterious because it happens only on one computer, on another the sound volume is saved OK.

The other mystery is that I have Ubuntu 14.04 and 16.04 on the same computer with the common /home. On Ubuntu 14.04 the sound is aved OK, but on 16.04 it does not.

What can I do to troubleshoot this issue?

I created a new user and found that sound works correctly with the new user. That means that something was wrong in user configs. I found some configs and it looks like the problem is solved. The files were not in text format and I have no idea what that format is.

I removed all files from ~/.config/pulse/ and rebooted. Now it works OK.

I also removed all files from /root/.config/pulse/ to fix 100% volume on login screen.

I think they've changed format of some config files in the new version of pulseaudio. The config from 14.04 confused pulseaudio in some way.

I saw some bug reports about this issue. It may happen when you replace Ubuntu versions with the same /home.

Update: This looks like a distro upgrading bug. I upgraded 14.04 to 16.04 on another computer, and there was the same issue.

cookie file needs to be removed in ~/.config/pulse/ after an upgrade.

Disable the "Keep Settings" in the PulseAudio Equalizer.