I have a neighbor bgp with my mpls provider. In some cases the number of prefixes that I receive is different that the number of prefixes that they advertise.
In the ISP's router:
sh ip bgp vpnv4 vrf xxxxx neighbors 126.96.36.199 advertised-routes | inc Total
Total number of prefixes 1380
and y my router:
sh ip bgp neighbors 188.8.131.52 received-routes | include T
Total number of prefixes 870
I've noticed you have :
neighbor 172.x.y.129 allowas-in
I think the default-value is 1.
this probably will not allow a prefix were your own AS number appears more then one as a result of AS prepending done on another site and reported to your local router by the PE router because is not using any form of as-override.
Hope to help