EP Function Buttons - no clicky clicky?

Hi all, just wondering if anyone has had a similar issue and found a solution;

just added one of the 128MB versions of the KO-II to my roster (I use 3 EP units in tandem at the mo) and have had to return not 1, not 2 but 3 units for having sunken or not clicking function buttons (the little buttons).

I know it’s not a biggie for everyone but for live play I need the tactile feedback…and they feel shoddy and failing for a new unit…has anyone found a way to fix these sunken buttons at all? None of my other KO’s (KO OG, 1320 and Riddim) have this issue and feel sturdy and tactile, so hoping there’s a fix!

Thanks in advance for any info