If you look where the lever is bolted to the main clamp/body , it seems that a teflon/plastic washer has worn and thus created some up & down movement in the lever, maybe a spare part can be found, i just dont know. I think by adding a couple of rubber or plastic washers to the bolt the play could be eliminated. It may be able to be sorted by screwing the bolt really tight, I just havent tired anything as the brake was intended as a short term solution for me so I just needed it to slow me down!
Other than that the brake works fine.