Needed this on a D7-to-D10 migration. I created a patch to add FileImportDesc to add description similar to the implementation of ImageImport adding alt/title/height/width. It can handle multivalue files provided you pass an array the same delta length into the descriptions line. Ends up looking like this:
field_files:
plugin: file_import_desc
source: uris
description: descriptions
skip_on_missing_source: trueCircling back: the fix on 2.7 seems to work for me. Note that I did need to run drush updatedb which ran add_service_definitions from memcache_admin to clear an error that appeared.
Seeing this same issue. It's causing issues on specific pages with Big Pipe as well because it is failing. Some kind of conflict, not sure with what yet, but reverting seems to solve the issue. I'm continuing research, but we're still running Drupal 9.x so I'm betting that is part of the issue an an update to core may resolve.
Pushing for a full release of this fix. Our sites avoid dev versions as potentially unstable, and this is playing havoc with our testing pipeline and requiring significant workarounds for non-production environments.