The plastic moulding is an issue. We have it on ours and I have to push it back in again occasionally but it's never come completely out or enough to bother us too much.
I went out and checked two of ours slides since four of them have the same kind of setup as the one you uploaded a photo of.
My rearmost roadside slide (bunk slide) looks to be just like yours and I've never messed with it as it seems to operate fine.
The slide just in front of that has the "bar" on the forward side of the slide but is quite a bit "tighter" yet still has obvious slack. I've never adjusted at of them and don't plan to unless I have to.
I wouldn't worry about yours unless you are seeing or experiencing some adverse effects.
I've uploaded photos of mine in the order discussed.
2014 Dynamax Trilogy 37BH
2015 Ram 3500 DRW