Let's face it, there are only two things that it could be, physical or mental. Could be a pinched nerve from sitting badly in a chair. Could be some kind of spazmotic pressure on the spine for what ever reason that comes and goes. With AD the sufferer can not communicate pain or other discomfortsa and symptoms appropriately enough to let you know just what it is and where it is coming from. You will have to play detective to try to locate what is going on. Just like that diagnosis stage it's self. Eliminate all of the physical things that the symptom can be, and what you are left with has to be mental. If it IS mental, then dollars to donuts it will be part of the AD symptoms.
My mother couldn't walk the last few years. But this symptom was on-going, and cronic. There was an actual physical reason for that. I was not part of her AD. However, all AD sufferers are different, and they can go through many more or less stages and symptoms than other AD patients.
I hope that this help a little, sorry but it's all I know; you'll just have to play detective, I guess.
Smiles,
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Gizmo