I have now shimmed the counterweights on both of my K-27's and inserted packing ABS "washers" on the 1st and 4th axles to reduce the amount "sideplay".
I found that all of the axles required some shimming under the counterweights and while I was at it, took some measurements.
I found that all the counterweight holes, measured from the flat of the "D" appeared to be the same. The issue is the machining of the flat at the end of the axle, they all verried to some extent, hence the need to shim.

In my opinion, replacing the counterweights would not solve the problem, the axles would have to be replaced with accurate machined locking flats.
Not an easy option.

Wayne