If its the same problem that Terry gets then I dont think its ever been found and if I remember the only way he could get things back up and running was a fresh install of Mach, but Terry will advise.
If however the DROs dont show this movement then it is not likely to be the same and although Terry says it cant be lost steps because it goes one way then the next that would only be true if it was at the apex, if it was not then it could well be lost steps.
So do you think the line goes off directly at the apex, from your pic it looks to me that it is before. Also looks to me like the line going up seems to be at the max height that the circle would be, so that does suggest lost steps to me.
Hood