yeah this has been bugging me for a while and i cant figure out if its a prop issue, a motor issue, or something in my tune. running a 4s 5inch on Hyperlite Elites 2306 2450kv and one of the front arms just feels slightly different in the air, kind of a subtle wobble that you can feel in the sticks more than see in the footage. ive already swapped the props on that arm twice and rebalanced on the stick balancer. swapped to a fresh set of HQprop 5x4.3x3 and still feels off.

blackbox shows a little more P term oscillation on that motor compared to the others but im not sure if im reading it right to be honest. motor temps feel roughly the same after a pack. frame is an older Armattan Marmotte that has definitely taken some hits but i cant see any obvious cracks.

anyone had something like this where it just ends up being a soft mount that shifted or something dumb like that

check if that motor can physically wobble at all when the prop is off ? like grab the bell and try to wiggle it. even a tiny bit of play in the bearing you'd feel compared to the others. ive had almost exactly this situation and it turned out the bearing was just starting to go, not dead yet but enough to throw off the resonance and mess with filtering. the blackbox trace you described kind of points that direction too if its specifically that one motor showing more P oscillation.

also worth checking if the motor mount holes have wallowed out at all on that arm, if it's taken hits the screw holes can deform slightly and give the motor a tiny bit of movement under load. had that on an old Chameleon frame and it drove me insane for weeks before i spotted it.

random thought but did you check the actual motor screws are all fully seated and the same length? sounds stupid but ive grabbed the wrong length from my parts bin before and had one sitting slightly proud without realizing. wouldnt cause huge issues but with resonance stuff even small things matter