I dont know if it has happened to many if any NMc's but i know of a fair few advanced people who have also done this, its the nature of trials and it sucks lol.
1) Get some money 2) go to Argos 3) purchase an angle grinder 4) take it home 5) get your wheel 6) plug in the grinder 7) put on some goggles 8) turn the switch on 9) pick up the grinder 10) skim it along the surface of the rim 11) keep doing this till all of the rim is rough 12) turn the wheel over 13) do the same on the other side 14) turn the swtich off 15) remove the grinder plug from the socket 16) remove your goggles 17) watch out for wires on the way out so you dont trip over
They feel horrible to be honest. No point in buying one because the levers wobble really bad, they feel no better , the lever blades are a bit harsh on the old fingers and the lever pin falls out all of the time.