I had an issue with my non Schwintek slide on my 2015 323LKTS. Mine was a problem with leaving a gap like you show only on the inside. After 10 trips to the dealer for adjusting, I finally got a referral to Lippert, who makes the slide. It was caused by a bowing in the female tubes which caused too much room and kept allowing the slide to get out of adjustment. My dealer had no idea how to fix the problem. But Lippert did in one service visit. I would have the dealer get Lippert in contact with you.
2015 Eagle 323 LKTS
2003 Ford F250 7.3 L Diesel