The rain slickened up the ground. One of my neighbors hired hands found that out the hard way. They were trying to finish picking corn a few days ago when it happened. The hired man pulled the truck into the field and saw he was sinking in a little. He whipped over onto drier ground and planned on heading out a different way than he came in. Unfortunately he was heading over end rows. End rows tend to be tricky because the trash from the picked corn is usually heavier than other places. That proved to be the case here and it wasn't a big spot. With both drive axles so close together, a slick area not much bigger than your kitchen table is large enough to lose traction. It does not have to be deep either, once the smooth wheels spin you better pull your cellphone.
Luckily my neighbor has a CaseIH MX305 that was able to yank that truck right out of the field. Check out the details on TractorData. Due to legal constraints (for the web pics, I did not take any of my own) I do not have any pictures to post.