ospf database size - affects that underlying transport mtu might have

This is a *single area* ospf environment, that has been stable for years.. But now suddenly is having issues with new ospf neightbor adjacencies , which are riding a 3rd party transport network Anyone ever experienced anything strange with underlying transport network mtu possibly causing ospf neighbor adjacency to be broken ? I'm asking if the underlying 3rd party transport layer 2 network has a smaller mtu than the endpoint ospf ip interface have, could this cause those ospf neighbors to not fully establish ? .and I'm also asking this if the single ospf area has grown large enough to cause some sort of initial database packet to be larger than that underlying 3rd party mtu is providing -Aaron