I know sleepy in later years had Lance 1162, that I own as well and they all share the same poor design.
In 1162 slide goes on driver side up to front corner and when they have steel channels here and there, the chanels are not connected in the corner, so that's where separation starts.
I went farther in my repair and not only welded the steel inside to meet in the corner, but added 3x3 aluminium angle all the way under the slide to reinforce the 3/4 x 2 piece of wood that was holding whole structure.
Lot of ways to make it work and my fix proved itself on 7000 miles vacations couple years ago.
At least you have your refrigerator board already upgraded.
Happy camping.