Yeah, mounting definitely makes or breaks these sensors. I had a similar headache with my metal window frames—thought I'd bought defective sensors at first. Turns out it was just interference from the metal itself. Ended up using some thick double-sided tape to create a small gap, and that did the trick. Honestly, though, it's kinda frustrating how manufacturers don't clearly warn you about this upfront. Aqara sensors have been mostly solid for me too, but I've also tried some cheaper no-name brands off Amazon... let's just say you get what you pay for. One set randomly disconnected every few days, drove me nuts until I swapped them out. Lesson learned: spending a bit more on reputable brands and taking extra time on placement saves you from constant troubleshooting later.
Totally agree about the metal frames causing headaches—seen it countless times. Another trick I've used is placing a thin plastic shim behind the sensor to reduce interference. Aqara's solid, but honestly, Ecolink sensors have been even more reliable for me, especially with Alexa setups. Worth checking out if you're still having issues.