3356 leaking routes out 3549 lately?

Has anyone had issues with Level 3 leaking advertisements out their Global Crossing AS3356 for customers of 3549, but not accepting the traffic back? We've been encountering this more and more recently, bgpmon always detects it, and all we ever get from them is there's nothing wrong. Today it affected CloudFlare's ability to talk to us. It seems to happen mostly with Europe and Asian peering points. Typically lasts five to ten minutes which makes me think someone working on merging the two networks is doing some 'no one will notice this' changes in the middle of the night. David