so anyway this has been bugging me for like two weeks now. picked up a BetaFPV Aquila 16 ? no wait not that one, the larger one, the prebuilt 3.5 inch they put out last year. flies fine in normal cruising but whenever i do a fast snap roll or a hard flip i get this oscillation at the end of the move, like its overcorrecting and then settling. its not horrible but its visible in the DVR and it just feels wrong.

i havent touched the PID tune at all, its basically stock. wasnt sure if i should start with D term or P or what. props are fine, checked them. running on 4S. dont really have a ton of experience manually tuning betaflight so im a bit lost on where to even start poking around

that kind of end-of-move oscillation is almost always D term being too low on a prebuilt. manufacturers tend to ship with very safe tunes that wont cause issues for most people but they leave a lot on the table. try bumping D up by like 5 on roll and pitch and see if that settles things down. dont go crazy all at once though, just small increments and test between each change. also worth checking if you have any prop wash issues on dives which would show up similarly and might point to the same thing.

if D doesnt sort it then look at your P term on roll specifically, sometimes the P is just too hot for that frames flex characteristics and you end up chasing your tail. but honestly start with D, thats the most likely culprit on a prebuilt with a stock tune.

had literally the exact same thing with my prebuilt toothpick a while back, drove me insane. ended up being a slightly bent motor shaft that i completely missed visually but you could feel it if you spun the motor slowly by hand. might be worth checking that before going too deep into PID changes, especially if you've had any crashes recently even minor ones