Thumbnails Not (Re)generating

Many of my FooGallery thumbnails are no longer displaying across more than 50 galleries. Console shows 404 errors for image URLs like:

https://dungeonsandtoast.com/wp-content/uploads/cache/remote/dungeonsandtoast-com/4232066505.jpg

The actual original images still exist and load fine at their normal paths (e.g. /wp-content/uploads/2024/07/Dog.jpg). It appears FooGallery is generating/storing thumbnail URLs that point into a wp-content/uploads/cache/remote/dungeonsandtoast-com/ folder, and many of the expected files in that folder are missing (only ~262 files present, but far more galleries/images reference paths in that folder).

What I’ve tried:

• Regenerated thumbnails (via Regenerate Thumbnails plugin) for affected images — reported success, but the gallery’s displayed URL didn’t change at all, still pointing to the same dead cache/remote/... path.
• Cleared FooGallery’s “Gallery HTML Cache,” “CSS Optimization Cache,” and “Thumbnail Cache” (multiple times) — no change.
• Ran FooGallery’s “Thumbnail Generation Test” — reported successful.
• Confirmed Thumbnail Engine is set to Default (not ShortPixel), and Imagick/GD are both supported and active.
• Toggled the global “Use Original Thumbnails” setting — saves fine, but doesn’t change the broken images’ output.
• Tested the per-gallery “Force original thumbnails” checkbox on one gallery — this does fix the display, switching the image to its standard WordPress thumbnail. However, this isn’t a practical fix across ~60 galleries (and I don[t want to render that many large images) per page.
• Searched wp_postmeta and wp_options for cache/remote and the broken filenames — no matches found, so the reference doesn’t appear to be stored as plain text in those tables (possibly JSON-encoded, in a different table, or generated dynamically).
• Renamed advanced-cache.php and disabled WP_CACHE in wp-config.php — no change.
• Suspected Media Cleaner (Pro) may have deleted files from the cache/remote/dungeonsandtoast-com/ folder as “unused,” but the affected file is simply absent from that folder entirely (never generated, or deleted with no record).

Question: Where/how does FooGallery store the reference to this cache/remote/dungeonsandtoast-com/ thumbnail path for a given gallery image, and is there a way to bulk-clear/regenerate these references across all galleries so they fall back to standard thumbnail generation (without manually checking “Force original thumbnails” on each of 60 galleries)?

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