Sorry to butt in here when you're waiting for a reply from Ludedor but i'm sitting at home with a storm wailing outside and nothing to do .. so let me try and explain it to you.
Impaction is a term referring to a blockage and if you're talking scorpions then that would most likely be a faecal blockage..Constipation would be a similar description.
If you type impaction in google you'll be able to find quite a bit about it but try typing "impaction in scorpions" and you'll be able to read a few posts from other scorpions keepers .. Basically though it's a theory the same as so many other theories that is based on an idea without any real proof to back it up ... The trouble is, scorpion somantics is almost none existent so all we can really do is guess our way forward to a problems source. However from what i can read it goes a little like this .. The scorp becomes constipated (possible reasons are genetic, parasitical, physical damage and stress) and can't release it's faecal waste..This builds up in it's intestinal tracts thereby creating pressure on other organs which eventually kill the scorpion. Alternatively it's intestinal tracts can rupture releasing faecal matter into the body which of course would be toxic to the body which also could result in death to the scorpion.
It's an explanation that bears the hallmarks of common sense and which therefore has been accepted as a possible cause of scorpion mortality..........waiting for the onslaught
A possible scenario for your scorpion could be this ... You noticed a brown stain on the side of your scorpion which might possibly have related to a rupture of some kind in your scorpion although you also mentioned it seemed to clear up after approx a week. A short time later you observed this brown mark had reappeared together with strange movements..You then changed the substrate as well as doing other stressful things and eventually your scorpion dies.....There's only one thing in my mind that speaks against this being a case of impaction and that is that you observe that the brown mark disappears...If it had ruptured inside and the brown mark you saw was indeed faecal matter then where did it go and how did it get better?
Yeh..all we can do MajorMorbid is guess .. That's why the best thing to do is simply make sure we provide the correct care and environment and hope our scorpions live out their lives healthily.
Unless a cause of death is obvious (a heavy object fell on it, attacked by another scorpion, acute dehydration or some other obvious explanation) we're all usually fumbling in the dark.
If you get another emp try and remember that they can easily go a month or longer without feeding (especially males!) and when they do feed it'll be one or two crickets, no more...A basic rule of thumb is this...put food items in the enclosure just before the lights turn off and if you notice the food item is still there the next day take it away and try again a few days later..If the same thing occurs then give it a week before you try again...If you're in doubt about anything (pre-moult, gravid, ill) don't feed or if you do then make sure the food item is already dead. Never leave crickets of roaches in with your scorpion for long periods...Ideally anything that is not eaten after being in an emp enclosure for one night should be removed the following day.
Scorps don't see that well at all and experience their world through the sense of touch and vibration...A content scorpion that isn't hungry will experience any kind of vibration as an annoyance..continual vibrations (any movement!) will go from being annoying to being stressful..Stress through longer periods can be fatal because as in humans, stress compounds other physiological factors.
Ok.....I'll stop here. The storm sounds as if it's picking up so i'd better get into my storm gear and see if there's any damage around the house...