Sorry, I forgot to provide this important information: I am using RUT955 with FW 06.08.05, which is currently the latest before the newest 7+ FW.
I am currently reluctant to change to the 7+ FW because of some issues with the handling of the WIFI access points by the 7+ FW. I will report another problem report on this at a later time asap. Except some minor issues the FW 06.08.05 appears in total quite robust and it is doing a great job in ~ 20 RUT955s in our company.