Question: dsolve numeric validity of output

Hi all,

I have a problem with dsolve. I have a 2-d (thin shell) theory which I am solving with Maple. For a Simply supported beam, there is no problem, it solution is more or less what you would expect. When I make 1 side as a clamped edge (x=0), there is a problem. The total result is 'ok', but it gives a peak in the 2nd derivative of Urn at x=0. This peak results in unrealistic stresses, etc.

I don't exactly know what the problem is. It seems there is a problem in the equations what causes the second derivative of Urn showing a peak. The equations are straight from the theory, I checked it several times for errors. Could this be a inaccuracy in the numeric dsolve solution of Maple?

Most important, does anyone has an idea how to solve this? I have increased the accuracy by increasing the digits, but I get exacly the same.

Maple result:

Urn:

d/dx Urn:

d^2/dx^2 Urn:

Also, the list with the output does not show the 2nd derivative of Uthetan, the 4th derivative of Urn and the 2nd derivative of Uxn. They are in the equations... is that a problem?