In case you're still having this issue, it's possible to remove chapters from your favorites through the developer console. Press f12 and paste this function into the console tab:
collection_remove("name-of-list", "name-of-chapter");
Replace "name-of-list" and "name-of-chapter" with the names given in the list and chapter URLs. For example:
collection_remove("favorites", "other-side-english");
This can be useful for chapters that aren't available anymore and don't display the add to list buttons. Similarly, you can use the following to add chapters to lists:
collection_add("name-of-list", "name-of-chapter");