I would fully support Nigel’s comments about the the front set of drivers.
The other item I always seem to find problematic is getting the fabricated return crank to sit at just the right angle. I am sure there is a knack to it but I find that I end up have numerous attempts to get it just right. I often end up over filing and it goes past the correct angle. Probably impatience on my part. You do have to ensure that it is well tightened though otherwise it unscrews itself when running. How do I know that…..?!