I have a yamaha 311h, I was playing around in Amplitube ultra tuner and noticed something weird with the tuning of the 4th, 2nd and 1st strings.
All of these strings are cycling in vibration compared to all the rest of the strings which have a very constant, flat response.
6th string, low E https://postimg.cc/NyF057P4
5th string https://postimg.cc/185FrFjg
4th string https://postimg.cc/dD6rknWM
3rd string https://postimg.cc/xXv08pRM
2nd string https://postimg.cc/sQqX7QZh
It's also pretty strange that at the 12th fret the tuning is very stable for the 4th string: 4th string, 12th fret https://postimg.cc/LY8m8rm5
Plus, 6th and 5th string are at +10 when fretted on 12th string compared to open string tuning.
What could be causing this and how to fix it please?