I hear what your saying, the problem could range from nothing to everything.
Starting from the vehicle configuration as I mentioned to all manner of issues including sensors, tranny or just plain wearing out.
My advice is drive another D2 that is set up the same and see what you think.
If it similar or the same as this one you just drove, then its likely normal and based on your posts, probably not the vehicle you really want.
If it very different then stay away from the first one and keep looking.
It is easy to have higher expectations of a vehicle you havnt yet owned, based on others comments and you can lead yourself into a purchase you will later regret and end up chasing others problems or doing mods you hadnt budgeted for. Take your time and dont buy anything hoping for more than what it is.
cheers

