Problems in Loiter with apm

Hello I’m having problems with the latest versions of APM fimeware using several different gps the same thing happens even changing several apm

When I put mode stabilize everything is correct without strangers.

Once switched to Loiter mode the Dron has many faults

1 the dron begins to descend and ascend alone
2 the dron begins to be very very unstable not able to be still
3 rtl is sometimes if it does well and others do not

E calibrated many apm never happened this, now if and not already because I use apm 2.8 and I use gps from 6m to 8m calibrated in many ways all the calibrations are correct everything is checked correctly.

This only happens with Loiter or Rtl

3.2.1 fw is the latest to APM, what firm are you using? It´s better to share log to find help from other users.