For some strange reason, sometimes we cannot do a VMotion. While trying to resolve this strange issue, we did found a workaround: disable and enable the VMotion port. Once that's done, manual VMotion and VMotion triggered by DRS is working again. So I made a Powershell script to find the interface where VMotion is enabled, disable it and enable it again. Pretty straightforward, but I wanted to share it anyway.