What is a safe recovery path after a failed Bower upgrade leaves dependencies inconsistent?

I maintain a legacy frontend project that still uses Bower (pre-2017 release) for dependency management. During a recent attempt to upgrade several packages listed in bower.json, the process failed partway through, and now the local component directory appears to contain a mix of old and new versions. Re-running bower install does not reliably restore a consistent state.

My constraints: the project cannot be migrated to npm or yarn in the short term, the .bowerrc file points at a custom registry that may no longer be reachable, and I am unsure whether Bower's cache is contributing to the inconsistent resolution. Bower has no documented rollback mechanism, so I want to understand the safest sequence for returning to a known-good dependency set without making things worse.

Specifically:

• Does bower cache clean followed by a forced reinstall reliably recover from a half-completed upgrade, or can it leave resolution in a worse state?
• Should the .bowerrc registry configuration be validated before or after clearing the cache, and what symptoms indicate a deprecated registry URL?
• Is there any documented way to pin the previous working versions while diagnosing the failure?