Unfortunately, unlike a barrow as an example, the quoit, when it eventually falls, isn't going to fall apart one piece at a time until being checked like it did the first time around. This time it is very likely to end up as an expensive jig-saw puzzle on the ground IMO, which, in reality, that comment isn't worth a light because I am not qualified to say so!
It has lost two of its three main stabilising points, one being replaced with a poor substitute. They are the ones that connect the front to the back and therefore allowing the front closure stone to move outwards to a frightening degree. Looking at the ridiculous angle of the capstone you would assume it will slide off backwards but quite the opposite is actually happening such was the brilliance of its initial construction when it was perfectly balanced! The capstone has been designed and planned to not slide backwards which it has achieved magnificiantly, but no provision was made for it to not fall forwards like it is! Whoever is standing behind it when/if it does fall eventually will be the one that walks away!