This sounds like it is likely a bug with the local runner - in general, the python local runner is unfortunately not as reliable as some other runners and is primarily meant to serve as a test runner. You could consider trying the Prism runner - https://beam.apache.org/documentation/runners/prism/ - which is a new portable local runner which should be more reliable and is receiving greater investment from the community.

Either way, if you run into issues I'd recommend opening an issue in the Beam repo - https://github.com/apache/beam/issues/new/choose