We have seen time and time again, where the chips on the bottles aren't set correctly, and they can cause errors like this.
Have you removed or inspected the K Toner detection chip ("ID chip" in service manual) to see if it's damaged? We've had success in reforming the bent contacts to get machines working again. Pretty easy to get to from rear. Swing controller out of the way, remove toner transport motor, toner bottle drive motor (K), and then your chip is right there.
As for the bottle getting "stuck", the Black toner cavity has an air duct (lighter gray material) that sits right above the toner bottle and directly underneath the output tray cover (dark gray material). We have seen that "duct" get warped or broken and cause issues with the Black bottle "being hard to insert or remove". Make sure that this duct isn't interfering with the bottle's movement (Picture attached for reference).
Bookmarks