On our last run our nearside re window seized solid. It turned out to be a fractured spring inside the winding gears. I had to break the metal tabs that hold the gear housing in place to get access to the mechanism. I was surprised to find that a spring was used to lock the mechanism to enable the window to be set at any position and stay there. I found a spring in my spares box that I could modify to fit. The arrow in the photograph below points to the broken end of the spring. The spring on the left shows how the catches should look.
The spring works by expanding into the barrel and locking the gear. When the window winder is turned to raise or lower the window the spring is tightened which releases the barrel and the window can move.
Having removed the spring and gear housing by undoing the bent over tabs I needed to rivet it back on for strength as the tabs had been weakened by my bending.
My box of spare springs.