I am running in to the same kind of issues with some additional factors.
FWIW, have you tried the following in this order? 1. stop the vpxa service on the host, 2. stop the vmware-vpxd service on the vcenter server, 3. start the vmware-vpxd service on the vcenter server, 4. Start the vpxa serivce on the host. Then try to re-add.