RE: What do you think would cause this
 

check the rest its probably off line because it seems to happen to me every year

RE: What do you think would cause this
 

Same thing happened to methis week. My arrow rest was too far to the right. I moved it back to center and the fishtailing went away.

RE: What do you think would cause this
 

Could be centershot off slightly or you are getting tailwhip from the fletchings hitting the riser. try moving the the rest out,recheck your clearance.