i was having the same problem , this has been awhile , it was driving me nuts . i sent it to martin i thought it had a cracked limb they set it back said it was alwright and it was but still had the same ping. i just kept shooting
the bow. one day i let my grandson shoot it so i could listen to it, wasn't as bad as when i shoot it but was still there. took it to my martin dealer and shop, the man has been shooting martins for about 50 years. he and another long time martin shooter both listened they both said it sounded like my quad arrow rest . i think it is the cam but not a 100% sure about that. would like to put a wisker bisquite on the bow & see if it is the rest don't have one. i also have another nemesis a 2011 the other is a 2010 . the 2011 has just a slight ping not enough to worrt about. and the 2010 seems to be getting quiter. to good of shooting bows to get rid of for a little ping .
2009 alien x camo, 09 x all black , 2010 x carbon fiber
2010 nemesis camo, 2011 nemesis carbon fiber,
2010 onza 3 camo,
2010 pearson legend black riser camo limbs