Redmi Note 9 Pro Max volume button bug

Guys i bought a Redmi Note 9 Pro Max, it’s having an issue with volume buttons! Like if i try to increase then it will decrease a step and increase back… And it i try to decrease then vice versa… But if I touch the and adjust the volume from UI then its ok!

Any idea about this? Is this a software bug?
How to fix?

Hmm sorry for the late update, I took it to the service center the next day. It was a hardware issue, they replaced the volume buttons as per warranty policy. Xiaomi products have quality issues nowadays.

How much it cause to fix

How much it cause to fix

How much they’ve charged?