bass drop off

[boogieslayer]

for sheets n giggles I ran a boss metal zone thru my mark IIc,...sometimes after a few minutes the signal still is there however it sounds like the bass drops out...what would cause that?

the IIC works fine without the pedal

 

[boogieslayer]

any clues why the bass drops off...

its kinda strange it doesnt last long ...if i turn the IIC off and wait for a couploe of minutes it comes back on...once or twice theres been a very slight crackle...couldit be it just needs a good blowing out and cleaning?
the amp as i said above works fine without teh metal zone pedal...
im stumped..