Arduplane Not holding Altitude

Archive
1

My APM does not hold altitude in FBWB and does not rise to 100 metres in RTL (in fact it Falls in altitude in both cases). See attached TLog.
RTL Location in Tlog Attached : 49% - 56% -: You can clearly see the altitude go from 50 metres to 15 where i had to enable manual again. RTL altitude is supposed to be 100 metres.
FBWB Location in Tlog Attached : 41% to 44% You can clearly see the altitude go from 30 metres to 8 where i had to enable manual again. FBWB is supposed to hold it’s altitude.

Something fundamentally is wrong here - ALL calibrations are complete.
Can someone help please ?

2

Would it be possible that this is caused by never completing automatic tuning ?

3

A dataflash log would be much more helpful.