I have the same issue. The eye level finder clicks into place but only, it seems, at the back. The front rises about 1-2mm. It doesn't fall off but it isn't right either. It feels like the front pin is just not engaged by the latch. The latch itself seems pretty straight and not obviously bent up in the middle like the one on the previous thread. If I take the focusing screen out, it latches better and sits flush with the body. But I can still pull the front of the finder up and it will move.
Have any members got experience of this and any possible solutions/advice to offer?
If you look at the photo of the front catch in the thread you link to you can see the bar is bent upwards in the middle, it should be straight. Check if yours is also bent.
Here are photos of the camera with prism gap showing, and of the front and rear latches. Also is a photo of the prism fitted without the focussing screen. It sits nicely flush but I can pull it up at the front. The focussing screen is a Type A. The pins are not rotated (flat sides up).
Okay - small update. Got a different focussing screen. Still A type. Seems to be slightly thinner and, when fitted, the prism finder sits flush with the body. Weird.