Rollei 35SE wobbles film back and battery question.

Hallo,
I have a few rollei 35 cameras.
Just purchased the 35SE and the film back while locked wobbles a little.
I tried to fit my Xanar 35 back but I guess they are different size.
The metal top looks straight. Everything looks brand new.
It just wobles slightly.
It might not be a big deal but my OSD is calling me.

Oh and any advice on the meter battery?
5.6 vs 6V
How is the down converting adapter?

Over 40 years, I've owned two 35S and two 35SE. The meter in the 35S uses a simple resistance circuit which varies the light measurement with changes in the resistors connected to shutter and iris, using the voltage of the battery as its base reference. Therefore, the voltage of the battery in the S is critical to accuracy of measurement. The meter circuit in the SE is not battery voltage dependent per my measurements. I think it includes a voltage regulator, like most newer cameras, which takes what it finds and delivers a constant voltage to the system, as this is probably necessary to operate the diode outputs. I have run four 357 lithium button cells, as well as a single 6 volt cell. The light readings are the same and match my calibrated Minolta spot meter which I use to validate all of my camera meters.

Mine seams to underexpose.
Is it normal for the door to move a little when locked?