After noticing this evening that my Kenmore 70 Series washer had "walked" backward about three inches recently, I moved it back flush with the dryer, only to discover that the front of the top cover is loose from the rest of the case, see pix:


It wasn't like this when I last did a load of clothes two days ago. Someone else used the washer, someone who habitually overloads the washer and uses higher agitate/spin settings than she should.
On each side there is a set of holes that look as if something (a screw, a clip or something) is supposed to go there to hold the top of the case onto the bottom part. What is supposed to go there? I lifted the washer up and looked under it and didn't see anything that had fallen off or out of it.
Also, when I took some clothes out, I noticed that the tub seemed to move around a easier than I remember it moving before (see pic). I can grab the agitator and make the tub bang into the front and back of the case without much effort at all. What could be the problem?

Thanks in advance for any help you can offer.
Model 110.20722991