Nope not yet (knock on wood)! Definitely do not want to test it as I’m sure it would mess up the locking mechanism. I typically don’t go up to the full 90 for certain movements if it’s difficult to slowly set them back down. If going heavy I usually do the equivalent lift using a barbell. I’m considering slowly adding a few very common weights I use in a rubber hex dumbbell to just have so I don’t need to constantly think about it, though I have standard plate loadable dumbbells that I can use, but they are a bit awkward especially when you put a pair of 25s on each side (the edge of the plate digs into my forearm), but they work well for back rows, but prefer using my adjustable kettlebell for those. So far never had a malfunction where a plate came loose with these dumbbells…seems like they did a good job with the design. Probably would not be ideal for commercial use but since it’s primarily only me using them they should last a good while…hopefully!