NameError: global name 'fs_values' is not defined

Buenas, estoy utilizando la version 4.8 de Tryton y al actualizar la BD me da el siguiente error, podrian darme una mano xf?

1430 139951454361344 [2019-06-03 12:32:58,456] ERROR trytond.convert Error while parsing xml file:
In tag record: model ir.lang with id lang_en.
Traceback (most recent call last):
  File "/home/luis/tryton/trytond/trytond/convert.py", line 449, in parse_xmlstream
    self.sax_parser.parse(source)
  File "/usr/lib/python2.7/xml/sax/expatreader.py", line 110, in parse
    xmlreader.IncrementalParser.parse(self, source)
  File "/usr/lib/python2.7/xml/sax/xmlreader.py", line 123, in parse
    self.feed(buffer)
  File "/usr/lib/python2.7/xml/sax/expatreader.py", line 213, in feed
    self._parser.Parse(data, isFinal)
  File "/usr/lib/python2.7/xml/sax/expatreader.py", line 320, in end_element
    self._cont_handler.endElement(name)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 508, in endElement
    self.taghandler = self.taghandler.endElement(name)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 294, in endElement
    self.model.__name__, self.values, self.xml_id)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 686, in import_record
    old_values, fs_id, mdata_id)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 768, in write_records
    if values != fs_values:
NameError: global name 'fs_values' is not defined
Traceback (most recent call last):
  File "/usr/local/bin/trytond-admin", line 6, in <module>
    exec(compile(open(__file__).read(), __file__, 'exec'))
  File "/home/luis/tryton/trytond/bin/trytond-admin", line 21, in <module>
    admin.run(options)
  File "/home/luis/tryton/trytond/trytond/admin.py", line 54, in run
    installdeps=options.installdeps)
  File "/home/luis/tryton/trytond/trytond/pool.py", line 163, in init
    lang=lang, installdeps=installdeps)
  File "/home/luis/tryton/trytond/trytond/modules/__init__.py", line 467, in load_modules
    _load_modules(update)
  File "/home/luis/tryton/trytond/trytond/modules/__init__.py", line 437, in _load_modules
    load_module_graph(graph, pool, update, lang)
  File "/home/luis/tryton/trytond/trytond/modules/__init__.py", line 261, in load_module_graph
    tryton_parser.parse_xmlstream(fp)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 449, in parse_xmlstream
    self.sax_parser.parse(source)
  File "/usr/lib/python2.7/xml/sax/expatreader.py", line 110, in parse
    xmlreader.IncrementalParser.parse(self, source)
  File "/usr/lib/python2.7/xml/sax/xmlreader.py", line 123, in parse
    self.feed(buffer)
  File "/usr/lib/python2.7/xml/sax/expatreader.py", line 213, in feed
    self._parser.Parse(data, isFinal)
  File "/usr/lib/python2.7/xml/sax/expatreader.py", line 320, in end_element
    self._cont_handler.endElement(name)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 508, in endElement
    self.taghandler = self.taghandler.endElement(name)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 294, in endElement
    self.model.__name__, self.values, self.xml_id)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 686, in import_record
    old_values, fs_id, mdata_id)
  File "/home/luis/tryton/trytond/trytond/convert.py", line 768, in write_records
    if values != fs_values:
NameError: global name 'fs_values' is not defined

Gracias.

Could you please report it to our bug tracker? It seems there is an issue with one of the latest bug fixes.