The multi-rotor uses RTK for altitude hold, but the hovering altitude in Loiter mode is unstable

We built a multi-rotor drone with the following specifications:
Weight: 840g
Wheelbase: 330mm
Version: fmuv3-4.4.1

The aircraft uses RTK positioning and, even in the FIX state, its altitude isn’t very stable in Loiter mode, especially during level flight. At times, there’s a deviation of up to 50cm. I’ve subsequently reduced both the speed and acceleration settings, which decreased the deviation a bit, but there’s still a noticeable fluctuation. The PSCD from the log doesn’t look good. I’ve adjusted the psc_ series parameters based on advice from experts on the forum. Can anyone help me figure out the reason for this? Much appreciated. Attached is the log.

2023-10-30 20-25-52.bin - Google Drive