Chosen Solution
Left shift is not working, after change the keyboard the problem persists. With USB keyboard this not happends. I change the flex trackpad cable with the same result
The MacBook Air 13" (Mid 2013-2017) Trackpad Cable won’t affect the keyboard issue. The issue is either within the keyboard its self or the trackpad where the keyboard plugs into. Review this guide MacBook Air 13" Mid 2013 Trackpad Replacement Jump down to Step 7 Either the keyboard cable is damaged here or the connection on the trackpad has an issue. Or, lastly the trackpad encoder logic is damaged which converts the keyboards signals (USB) to join up with the trackpad to the logic board.
