Static resources are deployed to /pf/resources/* for client managed resources and /pf/dist/* for Fusion generated resources. After August 2020 Arc maintains previous versions for 365 days.
Google is indexing the content of these folder and, after release of PB, requesting a resource for a version that is no longer retained will result in a HTTP 503., which continue to be indexed in Google.
In order to update Google crawling DB, can you enable 301 to the current live build for the ressources which leds to 503?