I had this problem with my '95 850. The tension spring was holding it tight against the stop, but it still did not move the arm close enough to the windshield for contact throughout the entire arc. I solved the problem by the "brute force" method of re-bending the drivers side wiper arm. I ran the wipers and shut off the ignition when the wiper arm was in the "problem area", then did it a little at a time, until I had contact at the extreme end of range. Not the most elegant solution, but reasonably effective.

For me, this issue was independent of any particular wiper replacement. If I subsequently found out that there is a difference in height between brands, I would probably believe it until I could verify; meanwhile the "fatigued aluminum" theory put forth by others here works for me. (I guess that means that I acknowledge that I will eventually need to replace my wiper arm, instead of re-bending... Ah well.)

Roger
'95 854T 178k
'87 245 266k