I found this window on our 2015 195RB to be rather difficult to open the first few times as well though nothing like what your describing. In my case the rivet holding the arm in place was catching on the opening the arm pushes out through. The opening seemed to be a little smaller than what was needed. After opening it a few times it seemed to smooth out and we've not had any further trouble. Perhaps pull the screen off so that you can get a better look at things.
Here is a picture - the green arrow is pointing to the rivet that was catching:
https://goo.gl/photos/fP95GRqxqD652Hgd6