I've also had this problem with a silicone dip tube on a 5l kegland minikeg. The silicone tube is meant to sink so it can be stored and served on its side. I've tried the keg upright and no issues. But I need it on the side for space reasons in the fridge. The pour keeps getting stuck because the dip tube is floating on the top (I know this as I tried it in a 3l clear PET bottle with a silicone dip tube on a kegland t piece). Was thinking a stainless steel nut on the end of the tube? Would rather not have to fiddle with this though.