Hello there !
To whose having that loose feel/creaking problem: Peek over the long side of the Z2 and see if your tablet is slightly curved, not absolutely straight.
With my Z2, it seems the display glass is just a tiny bit too small, putting some stress on the body, leading to that slightly curved appearance.
This might be the cause for the problem.
My Z2 did not produce any creaking noise right after unpacking - I knew this thread prior to buying the tablet, so I checked thoroughly for any creaking issues, especiallly on the right bezel side: Nothing at all, felt and sounded solid as a rock.
Issues started after using the Z2 for a few days. At the same time, the touchscreen issue also came up - but maybe that's just a coincidence.
So please give the creak a peek, let's see if there's any connection between body deformation and the issue at hand.
I am using the LTE variant, running v2.55.