Hello.
It seems that another configuration of OSTSESSID cookie can make better this trouble. Before two days I edited file bootstrap.php and I changed value of constant SESSION_TTL from one day to 30 minutes:
//define('SESSION_TTL', 86400);
define('SESSION_TTL', 1800);
From this time I am not ability to simulate this trouble.
Trouble is not caused by role switching from scp to user. Users report the trouble even if they are not using scp role (only user role).
I hope that this helps.
Thank You and best regards.