That's so frustrating. My guess is that technology will improve over time and that won't be an issue in the future, but it's quite inconvenient for you right now. It may also be possible that lower level reactions might be happening even when your sleep is not disrupted, that might be detected by the assessment instruments used in dedicated sleep study labs. It would be a gamble, though. You could ask one of those centers for their recommendation.

I don't know where you are located, @cmx, but you might also want to check out whether there are any providers of Deep Brain Reorienting (DBR) near you. It is a relatively new approach to trauma therapy that involves, among other things, helping people to release shock energy from the body that gets blocked from being released in the aftermath of overwhelming events. The shock occurs when a threatening, surprising or deeply unwanted stimulus is detected in the deep layers of a part of the brainstem responsible for keeping track of where we are at all times in relation to our environment (waking or asleep). It results in the release of noradrenaline that travels upward through neural pathways to the cortex (virtually waking us up, widening our eyes, alerting the nervous system that there is something going on that requires our immediate attention), and downward, via the spinal column, to ready the body for quick (defensive, if needed) action. The release of that energy in safe, gentle ways, can look like shakes, shudders, shivers, sudden jolts (looks like myoclonus) and can also involve waves of heat or cold, tingling. It can present in many ways. The good news is that releasing shock in the careful ways that are done through DBR can improve sleep for some people. There has been an encouraging evaluative study done with respect to DBR's impact on PTSD symptoms (in which sleep disturbance is a major player), but none (yet completed) on sleep specifically. Again, this is a new approach, but has the attention of many trauma therapists and neuroscientists. The book by Jaan Reitav and Celeste Thirlwell gives more detail, which is why I suggested it. That you had no obvious sleep difficulties after the tragic loss of your sister might have something to do with other reactions that can occur in the face of overwhelming events (structures in the brain and brainstem can also release endogenous cannabinoids and endogenous opioids to numb us when the pain would be too great to tolerate otherwise...endogenous opioids might make us fall asleep). As you are such an astute observer of your own experience, you might have a sense whether something like this might be helpful even in the absence of brain monitoring during your sleep, as a non-invasive intervention. Again, I wish you well with your quest to sort this out and get back to sleep.