New shifters, new gear set, wont lock into the lowest gear, progressively gets worse… wont lock into second lowest gear 2 weeks later.
Changed cable, changed cable housing, tightened cable, problem recurs, what could be the problem?
By the way this is Sensah group set and I will never buy anything from them again.
Could be a load of things really and hard to tell without looking at it.
Everything clean and tight? Derailleur hanger straight? Trim stops adjusted correctly?
Brand new hanger, brand new shifters and cassette and chain, cable and housing changed. 3 mechanics have all checked it and indexed gears, none know - so nothing obvious.
Maybe internal track, maybe shifter, maybe derailleur. The pattern of gear loss over time is most indicative.
FWIW Park Tools / YouTube videos help me with ideas.