Why is my Samsung galaxy s22 ultra volume button not working!?

Hi, My Samsung galaxy s22 ultra volume physical down button not working after water damage!

Volume up button and power button works normal!

And phone works normal too!

After tearing down found no corrosions on any connections or on board except some white colour of corrosion on the back upper left corner on housing but not on any parts or circuit board other then that everything looks in very good condition !

also Zoomed in with my other s22 ultra micro zoom Camera and found no signsof corrosionon any parts!

I have Replaced volume and power button flex cable with brand new flex!

And also i have Submerged motherboard in isopropyl alcohol for at least 2 hrs.

Tauch cleaned with isopropyl where possible with eurbuds and on every connection!

All air dried.

Still can't seem to understand why the volume physical down button don't seem to work?

Any suggestions pls!

I have not submerged the cables yet?

As I don't see any link between volume button and display cables!

Could it be the motherboard! ?

Can u help me with ASAP pls!