I have the same problem and posted with pictures with burnt connections.. Same answer from manufacturer.. In process of making new assembly using heavier contacts hand made. I'm using 510 phosphor bronze spring tempered, new copper plated steel studs, lock washer nuts and new phenolic plate. Original contacts were .020 thick 3/8" wide. New are .032 and 1/2" wide but ground down to 3/8" just at the tip contact area to fit in the commutator. More metal, contact area to carry the amps. Will update with pics. No one in town would touch this project. I trust my own handy work anyway. I'm retired from the aircraft industry. It's right or wrong belief! No maybe or gray areas. I bought a mini metal shear and break just to make these parts accurately. Double checked metallurgy properties on 510 phosphor bronze. Confident this is the way to go!
part available on ebay