You are right, I am so new to this I assumed that night splints are night splints (i.e., a thing vs. a concept). Anyways, we are in Ultra-Flex ... the hard-plastic with hinges that are adjustable. Long velcro straps across top of foot and around calf. Hard plastic exterior with softer more flexible plastic insert (I think this is a comfort thing?).
Our son has had night splints for two years now. We only recently started having the same problem. We just check in on him every night before we go to bed. If a splint is off, we put it back on. Don't know what else to do. Danelle