N.C.
My son went through similar sleep walking, but it was not consistent. However, we are not a "consistent" family. We didn't have truly set routines at that time of his life. We kept a close eye on him but sometimes my husband would have to physically keep him from walking outside at night or out to the garage. Sometimes he'd get in the shower with him to wake him up. He would sometimes recall and sometimes not. He seems to have grown out of it now, he's 16, the last episode was at age 11. He actually walked across the street to my sister's house at 1am. He also used to get really bad headaches. He had a sleep test done (he had sleep apnea), he had an MRI done, he had his tonsils out (it seems to have helped the sleep apnea--but not completely). I feel like I'm rambling on about this, but my point is that maybe a lot more people than we know have sleep "disorders" and they may just have to learn to deal with them or grow out of them. But I'd do all of the tests you can to rule out things you can control.