I realize the assumption is "operator error until proven otherwise" but you will just have to trust me that we know how to wind strings.
Unfortunately, that fix didn't work for us. We've tried the string slot, shimming the tuner (previous owner had put a popsicle stick between the back of the tuner and the headstock, unbeknownst to me, which only slightly helped) a million attempts at winding the string differently, different strings, the Fender Stealth String retainer, and so far the only remedy that has worked is zip-tying the A string to the D string behind the nut.