Hello,
As stated above, SEP 11.0 is primarily designed to use Computer Mode, with the option to use User mode if needed.
There have been a large number of cases where clients started switching to user mode unexpectedly in SEP 11.0 for various reasons, some of them have been fixed, some of them are by design.
It typically happens when a clients is either installed using a client package set to user mode by mistake or if a client is switched manually to user mode in the console, either way, if the user that is logged on that machine logs on to a different computer, it will switch it to user mode as well.
I am not aware of design changes for SEP 12 in that respect, however I have not yet encountered cases of this happening in SEP 12.
Again, this issue normally shows up if mistakes were made while creating install packages or managing clients in the console. They do not happen randomly (improvements were made in Ru6 in that respect as well if I remember correctly).
Hope this helps.