Add me to the "ditch the gemfan's" choir.
I've had brand new out of the bag 6030 gemfans throw a blade on 1806 motors with 3s. I've heard the 6045's are a bit better but I've yet to see a gemfan that was anywhere near as well made as any of the competition. If they throw blades on dinky little 1806's with 3S I'm not surprised you're having issues with them on bigger motors at 4s.
That could also explain some of your mysterious falls from the sky. The gemfans are so much softer they could be flattening out - just a thought.
I'd also say the gemfans could be part of why you're having props come off as well. I agree that the single direction with nyloc nuts is best...but I've also got the CW/CCW setup on one of my builds and have yet to loose a single prop off it. I do have a very hard time tightening gemfans because I tend to break the blades off before getting them as tight as I like to make them
I ordered some of those surveilzone props to try but they messed up my order and only sent me one set of props (I ordered like 6) and a set of 2.4ghz circularly polarized antennas I have no need for. They said they're reshipping my order but it hasn't arrived yet.
I'm a big fan of the "FC" props from himodel as a happy medium. They're stiffer and give better performance than gemfans but a bit more flexible than HQ's so they don't seem to break quite as easily. They're also more expensive than Gemfan's but less than HQ's. (I think myrcmart has the same props but I haven't ordered from them to confirm yet.) The one issue I've had with them is that the hub is full thickness and doesn't have the dished out spot like the HQ's so on motors with particularly short shafts it can be hard to get a nyloc to fully seat. The big problem with ordering from himodel (at least to the US) is that the shipping costs as much or more than the props unless you go for the slow boat and order a LOT of props. But even with shipping figured in they're cheaper than HQ's.