Sounds like you're having some weird networking issue. You're probably having one or more adapters with vmotion enabled that can't talk to some of your other vmotion enabled vmkernel adapters.
For troubleshooting I would dedicate a single vmkernel adapter living on the same vlan, in the same subnet. You can also use vmkping from the ESXi command line to troubleshoot this issue.
Best practice we should be consider a dedicate a single vmkernal adapter with vMotion enabled for the production environment right?