[ICOM] SM-8 Up/Down Buttons Erratic

[K4QT Dave]

Lately my SM-8 microphone's up/down buttons have become erratic when 
used on either of two Icom rigs. My SM-20 continues to perform 
correctly. Contact cleaner comes to mind as a possible fix but the 
buttons look to be sealed. Voltage levels also come to mind but I 
lack a schematic for the mic. Has anyone experienced this problem and 
if so, how was it resolved? Suggestions welcome.   Thanks & 73, Dave K4QT.