Joined: Jul 2015
Posts: 7,236
Likes: 3,142
From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
the Alta adapter allows installing a square taper BB onto a bike that has an old school single piece crankset... it won't help what we now know to be your problem.
your question is really: "why doesn't the stock front derailleur work correctly?" and i'd bet that an E-type mount Front der. is what the bike needs... just a guess.
example... this may or may not be the correct part for your folding bike... it is just to give you a concept of the E-type mounting...
search: .ebay.com/itm/226344804407 on Ebay