My older summa is year 2008 s120d, letters started to peel off when weeding because cutting was 1mm off at 100mm letters.. First i changed pinch rollers, didnt help. Tried to change coil setup, (we thought that the coil was getting lazier, but it didnt help either). Then i took the blade holder out and noticed that small round metal balls fell off when i disassembled it.. i thought ill just oil it up, but after seeing those balls, i ordered new blade holder. Problem fixed.. it was the bearing that caused all my problems