FWIW I think I've tracked down the cause of some of my edge lifting issues.
I've stopped using the Whitestone loca, and am using some Chinese sourced glue. This new glue sets to a hard plastic, rather than a gum, and this gives cleaner dust free edges and is easier to remove from the glass for re-application, as it peels off in a single sheet.
I've had a couple of instances where the edge has lifted, not dissimilar to the original post with both types of glue, and the most recent occurrence was just after using my phone in my wife's car cradle. This cradle uses a spring loaded mechanism to grip the sides of the phone, whereas mine just uses a gravity mechanism to hold it. I found that applying pressure to the side of the phone (not the protector) could cause the glue to come unstuck. The pressure didn't have to be that great, and it's obviously causing a little bit of flex in the frame and screen which, over time, the glue isn't strong enough to hold onto (it probably doesn't help that the oleophobic coating of the screen makes it very slick, and so the glue doesn't grip very well, although this does make it easy to remove).
My suspicion is that over time the constant flexing, even if it's not very much, causes the grip of the glue on the screen to start to fail, and that's what causes these lifts. Presumably any pressure on the sides of the phone, not necessarily those from a case or a cradle, could flex the phone enough. So gripping it tightly, or having it in a pocket could presumably contribute to the effect.
Cheers,
Steve.