Error posting since Dec 27th

The plugin had been working great until Dec. 27th. Since then, I have been getting this in the log file (for example):

[2024-12-31 00:16:30] handle_post called for post ID: 50140
[2024-12-31 00:16:30] Post is published and of type 'post', calling post_to_bluesky
[2024-12-31 00:16:30] post_to_bluesky called for post ID: 50140
[2024-12-31 00:16:30] Authenticating with Bluesky
[2024-12-31 00:16:30] Authentication successful, DID: <obfuscated>
[2024-12-31 00:16:30] Attempting to upload image: https://mysite.com/wp-content/uploads/2024/12/50140_generated_1735604188.jpg
[2024-12-31 00:16:31] Image uploaded successfully
[2024-12-31 00:16:31] Posting to Bluesky with data: {"repo":"<obfuscated>","collection":"app.bsky.feed.post","record":{"text":"","createdAt":"2024-12-31T00:16:30+00:00","embed":{"$type":"app.bsky.embed.external","external":{"uri":"https:\/\/mysite.com\/article-title\/","title":"Article Title","description":"Article excerpt...","thumb":{"$type":"blob","ref":{"$link":"bafkreicmze54vmxtzav2wtq4w6hqcgsnocfnyer5zjmvu3a6enxz655a6y"},"mimeType":"text\/html","size":8177}}}}}
[2024-12-31 00:16:31] Failed to post to Bluesky. Status code: 400, Body: {"error":"InvalidMimeType","message":"Wrong type of file. It is text/html but it must match image/*."}

I substituted the actual site identity, article title and excerpt in the example above.

Am I the only one getting this? How can I troubleshoot further?

I don’t believe I have any ability to change the payload that’s being delivered to Bluesky. No changes were made to the site, with the caveat that WP Core, plugins and themes auto-update.

The page I need help with: [log in to see the link]