HOLD Switch Issue

Hi! I have a problem and I don't know how to solve it:

I have two ipod classic, a 5g and a 6g. When testing with the iPod 5g, I noticed that the HOLD button does not work. I swap the back housing with the iPod 6g and it didn't work either, I assumed both switches are not working. But, connecting the back housing of the 5g to the 6g, I noticed that both switches work with 6g and both don't work with 5g.

How could I solve this issue on iPod 5g? Thanks!