When I open a PAWS notebook in the Hub, if the notebook is in a sub-folder of my home directory, the URL gets a RTC: pre-pended to the subdirectory name. It doesn't affect running the notebook but does lead to an incorrect PAWS-public link when use the PAWS public link button in the interface. For example:

• Generates: https://public-paws.wmcloud.org/User:Isaac_(WMF)/RTC:Annotation%20Gap/v2_eval_wikidata_quality_model.ipynb
• Should be: https://public-paws.wmcloud.org/User:Isaac_(WMF)/Annotation%20Gap/v2_eval_wikidata_quality_model.ipynb

I tested at least Chrome and Firefox but didn't go much further in trying to narrow down behavior other than verifying that it seems to happen with all of my folders so isn't specific to the example one above.