Locking tuners are only part of the system, the saddles, nut slots and trem spring consistency are potential areas of instability. I had Sperzels on Gretsch, they were fine, the Bigsby at the other end was where the problems lay, however. But I love Bigsbys, so I came up with ways to ensure a reasonably reliant return to pitch: lubricated nut slots; roller saddles and a little up pull on the bar when things slipped. On classic trem designs, I tended to use 4 springs and have it flat loaded for downwards movement only, but not always.