I've a 'new' Mamiya 6 [nonMF version] and 75mm lens and after a very short while I am just so happy with this camera.
I've been reading about changing lenses and knocking off the focusing. And because I'll shortly add a 50mm lens to the kit, I'm a bit worried about this statement.
Can any of you folks that have a 6 tell me if this issue is something to worry about?
Never heard of this issue nor experienced it. The thing to remember, of course, is that there is a curtain which must be closed in order to switch lenses. I suppoose if one forgot that and torqued the lens like a great ape.... hypothetically, then, damage could result!
You'll love the 50.
My advice is, if you see another 6 or 6MF body then pick it up, you might need a winder or something in a few years.
What keithwms said!
I have the 6 with the lenses you mention and even though I use the 50 the most, I do change frequently. Never have I experienced this problem, nor have I heard of it.
Don't know who wrote that changing lenses knocks off rangefinder focus. I've never had that problem with my Mamiya 7 system. The 6 system is great too. I can't imagine this happening to you.
You may find that the rangefinder is fine with the 75mm/50mm, but a little out with the 150mm and need a little adjustment. My M 6 seems fine with all three lenses. There is a cam in the body that is used to change the finder frame line when the lens is changed, but that does not impact on the focus. It would be hard to damage that without doing other damage to the lens mount at the same time.