RS2000CUSTOM,
2nd set of brass I have fitted in the last 6 months
sounds like your a bit rough on the change m8 !!
the steel ones are very expensive iirc , and the problem with them is where as the brass item sbreak the steel units just bend , i.e the teeth burr up and make selection impossible , make sure you got a good clean magnet in the bottom to catch the fillings if you do , then of course cause they dont break , the gear will then bear the brunt of the rough change !!
the solution ------
dog box !!