It has happened at least once to most of my plants in the raised bed, but on different occasions. I've been propping up the fallen plants with stakes, and that seems to have made many of them a bit more stable. The Havana 142 in the picture above weren't so cooperative. Two days ago, they flopped the opposite direction. Soon after I propped them up, they flopped in the direction shown.
The soil is pretty saturated at the moment, so that is likely part of the problem. The sun is expected to make an appearance this weekend, so I'm hoping that helps them stand tall again.