MMC seemingly take delight in leaving as much wax polish on the windscreen as with the body when delivering a new car. My second long trip involved sustained heavy rain and the windscreen was very badly smeered by the end of journey. I bought a bottle of cheap vinegar based window cleaner and eventually managed to remove the surprisingly thick coating which transformed the wiper action and view through screen.
Just out of general interest. I used a rifle trigger pull gauge to measure the Plus Six wiper arms spring force at the wiper blade.
The measurement right at the end of the wiper arm at the wiper blade was consistent on all three arms at 1.5 lb ( 0.6803 Kg ). This figure was recorded just as the wiper blade started to lift from the windscreen.
Gentlemen, Your two comments, taken together, would justifiably interest a Morgan sherlock.
Dave? Have you tried a few windscreen scrubs with a vinegar-based window cleaner? At this stage, if it merely caused a change, you two are on the right track. I am going to try it on my car this summer.
gmg
P.S. We can also idly muse that different souls wash the new cars on Pickersleigh Road. Some may allow products to slop over the windscreen and others may not, which would explain why some CX cars are afflicted and others not. At least, that could be a theory. Everything has happened in the last 115 years. There are many stories.