I can confirm that this fixed the issue (disable_agent_session_cookie = 1 in the database), I opened a support case and they provided the instructions. They said it is due to using Instant Clones with vGPU, since there is an extra reboot involved in that specific use case, it throws off App Volumes manager. It's too bad this isn't documented in the KB anywhere, since I imagine it's a fairly common scenario. Still applies to 2.16...
