It is likely N137US was released to service with aileron slack. The stainless threaded connector on the pilot’s side was “backed out” of its attachment to the brass junction. Nevertheless, the CAB found all cables attached on the pilot’s side, even though the tensioner side of the flexible cable had but 1/2 inch engagement. Lockheed's test of tension on the aileron connections produced a severed Stainless cable, at 2,000 pounds.
No information on the (connections) valve side of the tensioner, but it was continuous. Loose cabling is suggestive of removal of boost valve and boost unit in the shop. The valve end, a swaged ball fitting, is assumed to have its keeper in place, or the CAB would have noted it.
Without more information, including shop logs, boost unit assembly replacement protocol, and other schematics, we are left to critique the CAB. The actual work in design, maintenance, repair, and design considerations of aileron systems cannot be judged, no data to support any criticism is available.
Lockheed did simulate a fouled aileron, and analysed force required to overcome a trapped aileron, (trapped in this case by the wing flap). A reasonable theory of entrapment could flow from a scenario where the flap, being retracted after lift off, contacted the aileron and pushed it up, creating wing down. If the flap then jammed, the wing is producing a right turn, and the flap is creating chronic drag, perhaps the cause of low angle of climb, and lackluster airspeed. The flap would have contributed to right yaw, especially if the left flap had stowed.