Writing to BigQuery raises a TypeError "GlobalWindow -> ._IntervalWindowBase"

I have a pipeline that reads from a PubSub topic, does some transforms and then writes to BigQuery. The exception message is this: `Cannot convert GlobalWindow to apache_beam.utils.windowed_value._IntervalWindowBase`

You can find the main part of the pipeline here [https://gist.github.com/PlugaruT/4666406bd8792b7b196dc1519c8885a2](https://gist.github.com/PlugaruT/4666406bd8792b7b196dc1519c8885a2)

The first part is basically reading from Pub/Sub and then I apply this PTranform.

And here is the gigantic stack trace: [https://gist.github.com/PlugaruT/52bf3834eec95fd5cc5779d3332e1433](https://gist.github.com/PlugaruT/52bf3834eec95fd5cc5779d3332e1433)

I've tried to downgrade to 2.24.0 version but this is still happening.

Also, I can't reproduce the exception locally when I run the pipeline with DirectRunner. It's happening only when running on Dataflow.

Imported from Jira [BEAM-11252](https://issues.apache.org/jira/browse/BEAM-11252). Original Jira may contain additional context.
Reported by: PlugaruT.