Let me put this as urgent, then you go and look then disreguard...
My worry is, with 4 inches, you need to be very carefull. an inch or 2 I would suspect cable & easy fix... 4 inches, sounds pretty like "more too it" !?!?!
Id be looking for problems asap!
Id start with a visual inspection, in the 4 locations, where the cables are connected to the bottom edge of the roof, which is clearly visible if you stoop down and look up, at the edge around the roof section.
Make sure the cables are NOT pulling itself out of the frameworks or something, due to wet walls over the years.
Another harder check is the cable & pully in the bottom section's top of it's walls at the same 4 locations.
I dont know, just thinking out loud logically, it could be a pully broken, but all cables have "their own set" of pulleys they travel through, but front or rear side could affect the other side when out of adjustment or something wrong.
Food for thought:
My front cables are 2 times as long as the rear ones, so say we know that the cables over 15 years, had 3% stretch in a cable... What I think is, it means on mine, allows the fronts to be lower by 2 times as much, could be same for you.