Flipbooks re-appear after being deleted

So i decided to do some stuff in UN4 saved all assets, flipbooks. Now after i re-opened my project, it had some missing assets all over the place. It was no biggie because we are talking about 4 flipbooks. So i delete everything in my folder including the sprites.

I re-import the sprites into the folder and 4 empty flipbooks appear. I delete them thinking it was a bug, and proceeded exporting sprites. Same thing happened with empty flipbooks appearing. Even if i change the name it doesn’t do anything. It is like those flipbooks don’t want to be deleted.