From the photos, it looks like the white slide material peeled away from the black along the center of it. Yes/No? And the center of the slide top fascia appears to droop, as well. That, and the wood behind the side fascia is rotted and split. Looks like some serious water intrusion across the top of the slide. Using overlapping layers of 4" Eternabond tape along the fascia onto the top of the slide would address part of the problem, but if water is getting past the outer seals and then running down the back of the fascia, then that will continue to deteriorate. You should take a closer look at the outer slide seals to make sure they are deploying properly and not leaving a gap for water to run under, otherwise any repairs you make will be in vain.
If you haven't already, you might try contacting Heartland for some guidance on what to do, possibly taking it to their repair facility in Elkhart, if you can.