Erratic Pitch input

Looking at your logs I don’t see anything surprising.
Given that your are in Loiter flight mode, the drone is supposed to stop in place when you release the pitch input.

Plotted below are RCIN2 (red), desired pitch (blue) and actual pitch (orange), as well as GPS speed (green). Whenever you center the pitch input the drone leans in the opposite direction to stop. Actual pitch closely follows desired pitch in these maneuvers, so no problem there. After GPS speed drops to zero, pitch levels out as again. So I would say the cause for the “erratic bouncing” is the loiter flight mode.

However, you have a severe problem with vibrations including clipping. For reference: vibrations below 10 are good, below 15 are tolerable, above 15 are bad. Clipping is also very bad. Vibrations in X and Y are not perfect but manageable, mostly below 15. Vibrations in Z are brutally high, in peaks above 80(!), which causes the clipping.

The vibrations alone may be accountable for the high loss, but it can also be a case of needed barometer compensation as well.

Apart from that I found some not-ideal tuning settings:

  • you are missing IMU temperature calibration
  • ATC_THR_MIX_MAN, PSC_ACCZ_I and PSC_ACCZ_P don’t match MOT_THST_HOVER

I recommend to read and follow the How to methodically tune (almost) any multicopter using ArduCopter 4.4.x guide. Download the .zip folder with the param files from the guide, edit each file to suit your copter and upload them one by one as you read along. The guide tells you what to do and which file is needed at any given time. Do not skip any steps! All steps are essential for a good tune. Anything that might seem like a shortcut will result in a worse tuned drone in the end.