Database view is not working properly

When trying to view a dataset,

./bin/beat --prefix web_dynamic_data db view banca/1/Mc/dev_probes

I sometimes get this kind of errors:

Traceback (most recent call last):
  File "./bin/beat", line 33, in <module>
    sys.exit(beat.cmdline.scripts.beat.main())
  File "/remote/idiap.svm/user.active/lelshafey/work/beat_platform/beat.core/src/beat.cmdline/beat/cmdline/scripts/beat.py", line 160, in main
    return module.process(args)
  File "/remote/idiap.svm/user.active/lelshafey/work/beat_platform/beat.core/src/beat.cmdline/beat/cmdline/databases.py", line 402, in process
    return view_output(args['config'], args['<set_name>'])
  File "/remote/idiap.svm/user.active/lelshafey/work/beat_platform/beat.core/src/beat.cmdline/beat/cmdline/databases.py", line 355, in view_output
    json_data[name] = common.stringify(value)
TypeError: 'str' object does not support item assignment