Hello Robert,  Normally the cause for this is the standard release of 7.6 had a problem recognising different username types as the same user. Eg, We track users as Domain\Username  So if your User logged in as  Domain.local\Username or Username[NAME].com   We'd think it is a different User and so we won't spot the disconnected session.   We've long since fixed this issue. This hotfix needs to be installed on all your Connection Brokers and it will fix this problem. [URL]  Let me know how you get on, Andrew.
I have a situation that sometimes my connection broker version 7.6 does not reconnect a user to a disconnected session on a RDS host, instead it create a new session on other host in farm. Anyone has deal with that kind of error before?  Regard's, Robert
Reconnect to session - vWorkspace 7.6