Question: Odd results plotting a procedure with a varying parameter

I am getting such odd results from plotting a procedure that I call Q_opt1. When I plot the procedure at a specified set of points, the values produced and shown by plot look correct, i.e. my procedure Q_opt is *decreasing* in the parameter s.

This can be seen in the link below to the plot Q_opt1_Diagnostic1, in which I plotted the following:

>plot([Q_opt(0.4,0.01,0.5),Q_opt(0.3,0.01,0.5),Q_opt(0.2,0.01,0.5),Q_opt(0.1,0.01,0.5)],s=0..0.5,legend=["Actual value s=0.4","Actual value s=0.3","Actual value s=0.2","Actual value s=0.1"]);

HOWEVER, when I plot the procedure with s as the input variable in plot, i.e.

> plot('Q_opt(s,0.01,0.5)',s=0..0.5);

I get a plot of Q_opt increasing in s! What is going on?!

I posted an earlier example of this under the topic "Bug in Maple 9 plot?" and someone kindly replied, checked out my worksheet, managed to get the right plot, and suggested I used "restart," which I did.

What on earth can be causing me to get such different results from plotting the exact same procedure?

I also upgraded from Maple 9 to Maple 11!

The links can be found at:
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