Then chain keeps falling apart

drywall anchors

1) Replace the chain.
2) Adjust the travel of the front and rear derailer.
3) Make sure the rear wheel is set properly in the rear fork.

For the wide range of gearing on a MTB, the rear derailleur has to be able to adjust a large amount. If you shift into the smallest front chainwheel and the smallest cog on the rear (position 1), you'll probably see the chain is very loose and the rear derailleur is pointed back horizontally. Conversely, if in the largest front chainwheel and the largest rear cog, the derailleur will be pointed forward (position 2)
Couple things to do: 1) Avoid the gearing combination of the smallest cogs. Instead, use the middle chain ring and a larger cog (you'll have the same net gear ratio). 2) You can remove a link from the chain. A chain tool is about $10.00. You push the pin out through all but the last plate on two links, bend the chain slightly to pop those 2 links out (2 links = a wide link + a narrow link), then put the chain back together. This is only advisable if in position 2 there is some additional travel for the derailleur and in position 1, the derailleur has no additional travel. 3) Make sure your chainrings aren't bent, straighten (use a open-end wrench and gently pull the chain ring back to flat). This isn't likely b/c you don't indicate the chain falls off while shifting. 4). If the chain falls of the inside, screw in about 1/4 turn the inner limit screw on the front deraillleur. If the chain falls off the outside, screw in about 1/4 to 1/2 turn the outer limit screw on the front derailleur.

you need to make shure the chains fit the tire snug and then you need to put a rubber tension band (they usually don't come with the chains) you can get them at a walmart or auto parts store, about $2 for 2 of them and come with little s hooks that you secure to the chain, instructios are on the package, the rubber band you put on the chains on the outside of chains and it keeps tension on the chains so they won't be lose and fall off. hope this helps.

Buy a new one, repair is not an efficient answer.

Have you stripped the studs that hold the guide bar in position? It is the only thing I can think of unless the guide bar has worn down so much there isn't a deep enough groove to guide the chain

probally missing a cerclip on the linkage assembly

I thought the two parts would snap/connect together. They don't. Put the agitator on upside down over the "dogs" and their connector. Holding that together put the top agitator over the bottom. Carefully put over the metal connector inside the washer and connect the bult. The bult is what holds the pieces together.
To take apart initially I had to use a socket set with a long extension and a pipe over the racket handle to get enough torque to loosen the bult

I messed with it myself until it finally came apart, found the hidden golt and tightened it, thanks.

look for the nut in the needle holder and tight it.