unichr() arg not in range(0x110000) error (sometimes)

Hi, I got a very strange error but only twice out of ten or twenty of runs.

It's happening in a blank sketchpad, with no code and a duration of 500ms. So no code at all. I tried to google this error, but I couldn't find anything about it.

Any clues about what's happening?

I'm using 3.2.2b1 'Kafkaesque Koffka' in Ubuntu 16.04

Thanks!

The experiment did not finish normally for the following reason:

Unexpected error
Details

item-stack: experiment[run].practice_loop[run].trial_sequence[run].block_loop[run].trial_procedure_1[run].blank[run]
exception type: ValueError
exception message: unichr() arg not in range(0x110000) (wide Python build)
time: Tue Apr 24 15:15:45 2018
Traceback (also in debug window)

  File "/usr/lib/python2.7/dist-packages/libqtopensesame/misc/process.py", line 154, in run
    exp.run()
  File "/usr/lib/python2.7/dist-packages/libopensesame/experiment.py", line 439, in run
    self.items.execute(self.var.start)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 103, in execute
    self.run(name)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 122, in run
    self[name].run()
  File "/usr/lib/python2.7/dist-packages/libopensesame/sequence.py", line 51, in run
    self.experiment.items.run(_item)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 122, in run
    self[name].run()
  File "/usr/lib/python2.7/dist-packages/libopensesame/loop.py", line 341, in run
    self.experiment.items.execute(self._item)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 103, in execute
    self.run(name)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 122, in run
    self[name].run()
  File "/usr/lib/python2.7/dist-packages/libopensesame/sequence.py", line 51, in run
    self.experiment.items.run(_item)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 122, in run
    self[name].run()
  File "/usr/lib/python2.7/dist-packages/libopensesame/loop.py", line 341, in run
    self.experiment.items.execute(self._item)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 103, in execute
    self.run(name)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 122, in run
    self[name].run()
  File "/usr/lib/python2.7/dist-packages/libopensesame/sequence.py", line 51, in run
    self.experiment.items.run(_item)
  File "/usr/lib/python2.7/dist-packages/libopensesame/item_store.py", line 122, in run
    self[name].run()
  File "/usr/lib/python2.7/dist-packages/libopensesame/sketchpad.py", line 154, in run
    base_response_item.run(self)
  File "/usr/lib/python2.7/dist-packages/libopensesame/base_response_item.py", line 128, in run
    retval = self._collect_response()
  File "/usr/lib/python2.7/dist-packages/libopensesame/base_response_item.py", line 232, in <lambda>
    return lambda: self.clock.sleep(self.var.duration)
  File "/usr/lib/python2.7/dist-packages/openexp/_clock/psycho.py", line 38, in sleep
    core.wait(.001*ms)
  File "/usr/lib/python2.7/dist-packages/psychopy/clock.py", line 222, in wait
    win.winHandle.dispatch_events()  # pump events
  File "/usr/lib/python2.7/dist-packages/pyglet/window/xlib/__init__.py", line 1140, in dispatch_events
    self.dispatch_platform_event(e)
  File "/usr/lib/python2.7/dist-packages/pyglet/window/xlib/__init__.py", line 1169, in dispatch_platform_event
    event_handler(e)
  File "/usr/lib/python2.7/dist-packages/pyglet/window/xlib/__init__.py", line 1326, in _event_key
    text, symbol = self._event_text_symbol(ev)
  File "/usr/lib/python2.7/dist-packages/pyglet/window/xlib/__init__.py", line 1262, in _event_text_symbol
    symbol = ord(unichr(symbol).lower())
ValueError: unichr() arg not in range(0x110000) (wide Python build)