I had the same problem. One night the tube slipped off the attachment clamp. (I took a small wire and twisted it around the fittings so it wouldn't happen again). What I found worked for me. I took two pieces of VELCRO strap and wrapped one around the tube just above the knee and the other around just below my knee. I then pull up the tube between the top strap and my bag. This lets the tube fall slightly between my legs with no strain on the tube. I also make sure that when I go to lay down that my free leg goes under the tube when I bring my legs under the covers. This enables the tube to come under the blankets over my left leg to my right leg and up to the bag. That way I don't kick my tube. I had added some additional tubing to my drainage bag allowing me to lay the bag flat on the floor beside my bed. The hospital gave me a container to drain my bag at night but it was always tipping over. I find the bag laying flat on the floor works great for me and never have any spillage.
At night when I hookup my drainage bag to urostomy pouch the suction pulls the pouch tightly across my stoma and it appears that is forces the urine out under the wax seal then through the seal. It seem that no matter how I position the pouch this happens on a regular basis. I usually have good urine flow, but I'd do move a lot.
Is there a hard plastic device that snaps to the urostomy patch and has a spout that the nighttime drainage bag can connect to?
I really believe it is the suction from the night bag forcing urine out under skin pouch.