Some of the early gen DT levers had an easily broken "star" washer in the mechanism. If this "star washer" is broken and/or missing the amount of over shift and return to on center movement the lever goes through increases. If this happens then it's easy to end up adjusting the cable for a lever position that's not the true center position. Bumps, stress and frame flex will draw the lever from the thought was right position to the actually is right one, and the der pulley will now not be centered under the cog.

These levers can usually be set to a friction mode. If so how does the system work in friction? Andy