SOLVED: Question

[PEF0owsx2!@]

When I go into the "Edit images" dialog for movies, I sometimes get some error where it just keeps buffering forever and never adding the image. I don't know why it happens, I'm adding normal images like JPGs and PNGs. Closing and opening the dialog, reloading the window or restarting Jellyfin doesn't change anything. Last time this happened I had to reset Jellyfin and start from scratch to fix it. I couldn't find other threads for this, but to be fair, my searching skills aren't the best in the world.

Is there a way to fix this without resetting? Like deleting some cached data or configs mayhaps?

Edit: The file I uploaded was named "poster.en.jpg" and I selected it as a screenshot, because I have another poster in my native language already added.