So I have a recently purchased RZ Kit ( RZ67 Mk1 + 110mm 2.8 + 180mm 4.5 , PD Prism ). I haven't had the time to shoot with it a lot since I got it ( a few months back ) but today when I mounted it on a tripod with the 180mm mounted, I saw the whole bellows rail was a bit wobbly on a vertical orientation. Here's a link to a short video I shot with my iphone - you can actually hear it clicking when I try and lift the lens :

So mounted on a tripod - fully extended - if I grab the lens from under it and lift it - I have a pretty obvious movement visible in the WLF too.

The camera works great, is in great condition - this only occurs when the bellows are fully extended ( or close to fully ) so kinda in macro mode - which I pretty much never use but I am curios if this is normal, maybe something is loose on the inside etc