During upgrade ConfigAndLog has errors about crm-l10n.js for every upgrade step because assets aren't built during upgrade
I'm thinking it started when this changed: https://github.com/civicrm/civicrm-core/pull/20121. The timing seems about right too.
The problem is CiviEventDispatcher::dispatch ends up dropping the hook_civicrm_buildAsset because it's not in the list of hooks that run during upgrade. This doesn't seem to cause any problems during the upgrade but then AssetBuilder::render throws an exception which AssetBuilder::build logs.
Maybe if there's a way for AssetBuilder to know if it's during upgrade and then be cool about it?