Foris interface is slow, runs to timeout

Using using Omnia, currently running OS 3.9.4.

Since 3.9.3, I think, the Foris interface loads quite slow.
When login to Foris always get the the following warning:

Even more navigating in the menu typically activates the certain page very slow, if at all.
In later case (runs to timeout) the following error is shown:

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/foris/middleware/reporting.py", line 92, in __call__
    return self.app(environ, start_response)
  File "/usr/lib/python2.7/site-packages/bottle_i18n.py", line 68, in __call__
    return self.app(e,h)
  File "/usr/lib/python2.7/site-packages/bottle.py", line 979, in __call__
    return self.wsgi(environ, start_response)
  File "/usr/lib/python2.7/site-packages/bottle.py", line 954, in wsgi
    out = self._cast(self._handle(environ))
  File "/usr/lib/python2.7/site-packages/bottle.py", line 862, in _handle
    return route.call(**args)
  File "/usr/lib/python2.7/site-packages/bottle.py", line 682, in mountpoint_wrapper
    body = app(request.environ, start_response)
  File "/usr/lib/python2.7/site-packages/bottle.py", line 979, in __call__
    return self.wsgi(environ, start_response)
  File "/usr/lib/python2.7/site-packages/bottle.py", line 954, in wsgi
    out = self._cast(self._handle(environ))
  File "/usr/lib/python2.7/site-packages/bottle.py", line 862, in _handle
    return route.call(**args)
  File "/usr/lib/python2.7/site-packages/bottle.py", line 1740, in wrapper
    rv = callback(*a, **ka)
  File "/usr/lib/python2.7/site-packages/foris/utils/__init__.py", line 67, in wrapper
    return func(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/foris/config/__init__.py", line 547, in config_page_get
    return config_page.render(active_config_page_key=page_name)
  File "/usr/lib/python2.7/site-packages/foris/config/__init__.py", line 465, in render
    foris_conf = client.get(filter=filters.create_config_filter("foris"))
  File "/usr/lib/python2.7/site-packages/foris/nuci/client.py", line 163, in get
    data = netconf.get(filter=("subtree", filter) if filter is not None else None).data_ele
  File "/usr/lib/python2.7/site-packages/ncclient/manager.py", line 89, in wrapper
    return self.execute(op_cls, *args, **kwds)
  File "/usr/lib/python2.7/site-packages/foris/nuci/client.py", line 113, in execute
    raise_mode=cls._raise_mode).request(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/ncclient/operations/retrieve.py", line 65, in request
    return self._request(node)
  File "/usr/lib/python2.7/site-packages/ncclient/operations/rpc.py", line 294, in _request
    raise TimeoutExpiredError
TimeoutExpiredError

Besides the Foris webinterface, the Turris Android app also runs to timeout.
Meaning it goes to infinite “Connecting…” loop.

Besides this issue, the device is functioning normally. Including Luci, SSH, and all the other services (Samba, Transmission, etc.).
Any idea?