Sudden gain in altitue in Loiter and alt hold mode

ArduCopter Copter 4.1
1

I have a Quadcopter with :
Holybro Duranal FC.
750 mm Frame,
17" propeller
Motor 5828 GARTT ML5008 330KV.
Battery 2 x 3S 5500mah to form 6S
Recently build but getting sudden gain in altitude in Loiter and alt hold mode.
Log file is also attached.
I checked the log and found some unusual Current and Voltage spikes in the battery section.
Can I anyone check & guide.
Thanks in Advance[Uploading:

https://drive.google.com/file/d/1EOJTqlArM_XgfQYnM_0pM6GIKF89_2HH/view?usp=sharing

2

The only altitude gains I could notice seemed to be desired and seemed to match throttle input. Can you describe the situation better?

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I do admit I couldnt really figure out what was going on with the voltage and current spikes, they didn’t seem to match up well with any particular actions or events. Maybe there is a motor or ESC going faulty?