Mamiya 7II Viewfinder

Hi. I was wondering if anybody could help me. I recently bought a Mamiya 7II with an 80mm lens, both second hand, from an established seller. The viewfinder has been bothering me a lot as it's got one square inside another. Sometimes a few lines in the outer square fade away but not complexly. I'm attaching a picture. Hopefully it can show best what I mean. I was under the impression that the square suitable to the lens would remain and the other would fade but it doesn't happen. I bought a new battery today just in case but nothing has changed.
Can someone please suggest what might be the problem?
Thank you very much.
juno

There are frame lines for 65mm, 80mm and 150mm. It may be that the mechanism that should show you the one corresponding to your lens is showing the 65mm as well, maybe not fully hence the faintness and variation. Try removing the lens and remounting. Otherwise I'd say that it needs some adjustment.