My setup is fairly simple, i dont really know where to look...
M7i border routers, one with a Fast-E to Mizma and GLBX and one with Sprint Fast-E, they both run IBGP with BI4k (jetCore), out to L2s. I have seen this issue across both the Mzima link and the GLBX link, the only common thing with them is they are on the same router and 4 port PIC card, and they both travel via a L2 MPLS link to Ashburn, VA via the same transport provider.
Brendan