VMs will only create up to two macvtap (vnet)

Hey,

so If I start a third VM I get this error:

Error: Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/middlewared/plugins/vm/supervisor/supervisor_base.py", line 152, in start
    if self.domain.create() < 0:
  File "/usr/lib/python3/dist-packages/libvirt.py", line 1234, in create
    if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirt.libvirtError: error creating macvtap interface macvtap0@enp1s0 (00:a0:98:29:2e:50): Device or resource busy

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/middlewared/main.py", line 137, in call_method
    result = await self.middleware._call(message['method'], serviceobj, methodobj, params, app=self,
  File "/usr/lib/python3/dist-packages/middlewared/main.py", line 1215, in _call
    return await methodobj(*prepared_call.args)
  File "/usr/lib/python3/dist-packages/middlewared/schema.py", line 1022, in nf
    return await f(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/middlewared/plugins/vm/vm_lifecycle.py", line 46, in start
    await self.middleware.run_in_thread(self._start, vm['name'])
  File "/usr/lib/python3/dist-packages/middlewared/utils/run_in_thread.py", line 10, in run_in_thread
    return await self.loop.run_in_executor(self.run_in_thread_executor, functools.partial(method, *args, **kwargs))
  File "/usr/lib/python3/dist-packages/middlewared/utils/io_thread_pool_executor.py", line 25, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/lib/python3/dist-packages/middlewared/plugins/vm/vm_supervisor.py", line 61, in _start
    self.vms[vm_name].start(vm_data=self._vm_from_name(vm_name))
  File "/usr/lib/python3/dist-packages/middlewared/plugins/vm/supervisor/supervisor_base.py", line 161, in start
    raise CallError('\n'.join(errors))
middlewared.service_exception.CallError: [EFAULT] error creating macvtap interface macvtap0@enp1s0 (00:a0:98:29:2e:50): Device or resource busy

I have a bridge connection to my NIC and between my VMs. Otherwise, the VMs can't talk to the host and vice-versa. So all my VMs NICs are attached to the bridge. If I start a VM they will automatically create a macvtap, but only up to two. 

Seems like the VM wants to create another "macvtap0" but this one already exists. Should be "macvtap2", in this case.