Remove the forend spacer and flat sand the flat side, test, repeat until the forend just slips on with little pressure to no pressure, that should reduce the vertical stringing.
On the pin, unless they have oversize pins available which they apparently don't, remove the barrel from the frame, remove the pin enough for the splines to just clear the frame, degrease the splined area of the pin, apply a tiny bit of JB Weld to the spline area, let it cure, then install it, should be enough to hold it in place. If it doesn't work, you're only out the time and effort.
I wonder what they did, maybe peened the pin hole before they refinished it?? If you tear it down, you may be able to do the same thing on the inside, the JB wouldn't require a tear down I don't think.
Tim