So, as a temporary workaround, I just removed all the resource pools using the vim-cmd over SSH.
- vim-cmd hostsvc/rsrc/vms_get pool0/pool1 (get list of VMs associated with the resource pools)
- vim-cmd vmsvc/unregister XX (unregister all VMs associated with the resource pool)
- vim-cmd solo/register XX (register VMs again which are automatically assigned to the default resource pool (ha-root-pool))
- vim-cmd hostsvc/rsrc/pool_config_get ha-root-pool (to check that all resources are assigned to the default resource pool)