And you are sure that these login credentials are not used on any other device?
Behaviour as you described usually looks the same if two or more clients try to connect with same credentials at the same time (which is not supported with standard remote access licensing, only with RA premium). the devices then keep kicking each other endlessly.
Can you please clarify what you mean by login credentials are not used on any other device? For instance I'm still logged into my workstation at the office, and I use VPN nightly and have never experienced any disconnect/reconnect issues. Is this problem only when more than one VPN connection is established at the same time?
Today I was offsite and noticed that all 5 users with laptops kept getting this disconnect reconnect problem. I thought initially it was because of the very flaky internet, but then I stumbled onto this post. Basically what we did was took with us the user's laptops to do some testing, and provided the users with loaner laptops. At the time of when I was experiencing this problem they could have very well been connecting with their loaner laptops at the same time at another location.