Nuts are falling out of place

that is a typical issue Seshan is correct.
You z adjustment screw is currently set so that the nozzle makes contact with the bed before the z endstop switch is activated
OR
the switch is already in teh activated position and you the boards didn't know that and you tried doing a home again and the z stop tried to lower even further thatn where it was leading to the first issue.

What ever you do do not try to secure or lock those nuts in place it is a saftey measure and they need to be free to do exactly what they just did the phrase that has been going around to describe it is "throwing you nuts" cuz it drives ya nuts when it happens.

There is a good process I can go through with you if you want to get you all set upand printing if you want the helpif you skype it is easiest and you can find me at Jeff Janes or jj.tesseract just send a contract request letting me know who you are. I have helped several people out here with great success they were up and knowledgeable about priniting a very short period and their prints are now really good

If you do not use skype you can always PM me here on this forum it is a bit faster than here but not too much

Look forward to seeing some nice prints