I'm having the same problem as this member: https://premium.wpmudev.org/forums/topic/unexpected-user-role-change
I'm running your Google Analytics, Ultimate Branding, and Snapshot plugins, as well as Dashboard. I've temporarily disabled the dashboard plugin and it hasn't reverted back within the past 30 minutes, but previously it had been reverting back every 30 minutes. I'm able to fix it each time by editing the usermeta table in phpmyadmin, but it's quite the hassle. I'll let you know if it reverts again. For now it appears to be related to the dashboard plugin.