Recently, I was trying to delete snapshots on ESXi and ran into some problems. When I deleted the snapshot, vSphere snapshot removal was stuck on 95%. I found some nice articles from VMware on how to resolve this, such as (1), (2), (3).
I was starting to get errors such as: "unable to connect to the mks: error connecting to /bin/vmx process" and the VM will not start.
I decided to delete another VM on the same PM in order to free up space for the VM stuck with 95% snapshot completion. That helped resolve the problem.