We have absolutelly the same issue.
Not only with Flex10. I got this case because of vmotion performance troubles. Nevertheless the average migration duration is absolutely OK, particularly with our DL980G7 hosts we notice dramatical vm freezes during vmotions. Allthough we use a dedicated 10Gb NIC-Team directly connected to the NEXUS Cores for vMotion some VMs experience sync lags up to 40 seconds and worse. That's absolutelly inaccaptable. We are only allowed to migrate VMs at late evening.
I'm not really sure this problem refers to the "RX Packet Drop" topic, but after some days of debugging time and no outcome I have to clutch at every straw 
BTW: Greetings from Bergheim @Jo
Manuel