Hi,
Have you configured the timeout setting of disconnected session when deployed RDS environment?
Kindly try to extend the time limitation and verify if the problem persist.
[Forum FAQ] Restrict number of Active Sessions in RDS 2012 and 2012 R2
https://social.technet.microsoft.com/Forums/lync/en-US/00c2252b-8ec0-489f-8da2-07a434a9b5a2/forum-faq-restrict-number-of-active-sessions-in-rds-2012-and-2012-r2?forum=winserverTS
Hope this helps and please help to accept as Answer if the response is useful.
Thanks,
Jenny