Yeah this is a kind of quirky situation that I haven't seen, but apparently it has to do with the first 2 constraints in your solve block. With the original assigned values, these two constraints are numerically identical. When the algorithm then begins to tweak sigma-z these two constraints...
When you consider that the find() function returns a vector containing values measured in different units, it makes sense to disallow units in that vector and hence in the quantities of the solve block. I'm letting you research this and tell me if my reasoning is correct.
Also Mathcad doesn't understand your units. I had removed the units and fixed the assignment and got it to work. Putting the units back in broke it again. I've never used units in a solve block but not saying it shouldn't work. I would say research the Mathcad utilization of your units
Your first assignment statement E = erroneously uses the boolean equate instead of the assignment or definition operator := like you correctly used elsehwere.
I did boot into safe mode and the surface plots started working, with what I would call questionable quirks, such as wacky background pixelation occasionally, but it is usable.
I'm running version 15 on Windows 7. I notice from a couple of years back other users have had trouble with surface plots but what seemed to work for those users (toggling the borders on/off) has no effect so I'm stuck. It's not my doing either; the quicksheet examples are not plotting. I just...
