Out of curiosity, have you checked your error logs recently? Sometimes there’s treasure in there.
That’s a pretty strange bug! The first thing that pops to mind is that the post loop is using a global $post variable that you’re not expecting, but that is obviously not the case – the rest of the slide info seems to be showing!
Can we assume that $slide = get_field('slider', $post->ID); or something similar? And are you using two different sets of code, or is the PHP/MySQL just being served to 2 different URLs?
