Thank you for your post.
Since this "does not happen to all the layouts", the issue could be a damaged layout. Therefore, create a new layout (do not duplicate the original layout as you may duplicate the objects that are corrupt), add a few fields and save to PDF. Does this open properly? If so, add a few more objects and save to PDF again. Repeat until you narrow down the object/field.
Keep me updated with any progress.
Thanks, I did as you said and now it opens fine.