It could be breeding related if your cool side temps are higher than the snake is looking for, they don't always know what's best! My submarine snakes do it year round, I just caught the girl who got an RI last year with her head and neck in her bowl this morning. She just loves to soak and I can't do anything about it other than give her a small dish. I'm not worried about her only getting a small amount of her body in the bowl. I'm not sure how big your soakers are, but I use small crock dog bowls for my adult soakers. For young ones, those little souffle dishes.
I talked to a couple different breeders and they agreed her soaking in the water so often was probably the reason. She and the male breeding her were the only snakes that got RI last year, she made it through treatments, he didn't. On top of smaller bowls I'm also keeping my cool side at 75 degrees this year to help avoid any RIs. I've always kept it at 70 degrees in the past.