The latching mechanism is attached by cable to the lever in the inside of the car on the LHside rear.
Maybe the mechanism needs oiling? Does it move when you move the lever? If yes it could be out of adjustment.
The curling soft top has been discussed on here.
I suggest you use Search look for something like 'soft top'.
Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto