been there , i bought whole new cutting head for my old 120D. It could have been repaired (something macgyver would do) but i didn't take the risk for breaking again. It broke ... 2-3 years ago and i guess i paid something like 1200-1500 euros for the whole head. The cutter was 5 years old and i thougth there was something wrong with the coil also.. pressures seemed to change a bit during extremely very long runs so new head was at my mind before breaking
It takes like 15-20 minutes to change the whole head for yourself.