hi - not sure if this helps anyone but I just had a problem with a brand new Altus SL-M370 front shifter where during fitting it jammed so I couldn't downshift? After taking the covers off I realised that it was being blocked by the adjustment screw in the "Cable Adjustment Barrel Unit" (the bit where the hose goes into the shifter) which I had screwed all the way in, I just unscrewed it a little and the shifter started working again. Seems like a design fault that if you screw it in too far it jams the mechanism but at least I'll know in future.