I'm a relatively new pilot and I'm troubleshooting blackbox weirdness. My motors are somewhat noisy on the bench, and although I don't have too much gyro noise in blackbox I do have a regular low frequency oscillation on all 3 axes, most prevalent in pitch and roll D terms, as well as high frequency jagged oscillations in all 3 D terms at low throttle (equal or less than enough to hover).
I've played with the PIDs and it seems that the cause is external - motors perhaps. I'm wondering how often everyone is changing motors after crashes? I never tested my motors on the bench when I first built the quad, so I don't know if they were ever clean, but I've crashed a couple times and can't believe that the motors would so easily sustain enough damage to affect balance. Maybe my props are too invincible? They don't break, only bend, and require a lot of force to do so (King Kong 6045).
Once I crash landed on a metal roof and clearly bent one motor shaft. The prop was bent, not broken, and lost a C clip off the motor. Replaced it but maybe needed to replace a second one as well, as the other motor on the same side has a faint grinding noise. Other than that my crashes have been relatively low speed, low altitude, into grass. Recently I did roll a bunch through grass and skid across pavement but again, just a bent prop and no obvious damage otherwise.
Like I said about PIDs, I've got my I and D down to almost zero but my D still has a lot of noise even though my gyros aren't that noisy. My P is kinda low and still gives me big wavy oscillations at higher throttle so doesn't seem like I can increase it any more to provide more authority. Also, the accelerometer in my motors tab flickers a bit with the motors off no matter how I calibrate it.
Setup:
Armattan f 1 6
DYS MR2306 2100kv
DYS XM20A
Seriously Pro Racing F3
king kong 6045
FPV setup etc...
4S batteries
I can provide whatever other information might be helpful, such as blackbox logs/screenshots, motors tab, etc.10.0.0.0.1 192.168.1.254

I will focus on the mechanical side of things first. Ignore blackbox for now as Betaflight will fly almost any quad on defaults. Never tuned a quad out of 6 builds.

- Check frame for any de-lamination, cracking, extra ordinary flexing, screws, standoffs, motor screws (snug and not touching windings)
- Check motors for smooth/notchy movements, smooth bearings, excessive runout on motor shafts, magnets, dirt in the bells, etc
- FC mounting, wires touching the gyro chip, any loose components such as a camera or vtx or antennas
- Connect the quad to Betaflight and rotate along all 3 axis and ensure you have no jittery movement
- Roll back to Betaflight default pids or try UAVTech's pids/filter presets: https://theuavtech.com/presets/
- Try a new set of props and ensure blades are at the same level (not bent)