Very common problem with several threads covering the topic. Ours is at Jayco factory right now getting the same thing fixed. They will be welding some gussets in the slide area. I don't know how much, if any, of the side wall they will be removing on ours. Another problem that is common and may be related to this is the corner molding below this crack separates and needs to be reinforced with bigger screws. Ours is having that done too. It doesn't appear that you have that problem yet., But you should watch for it. Plenty of posts about this issue too.
Ford F250 6.2 Gas, 4X4, Short Bed, Companion Hitch
2019 Jayco 28.5 RSTS, MorRyde orbital pinbox.