Using ContourPlot3D with extrusion in Printout3D

Question

I am joining two 3D contour plots using the Show command, and then I want to use Printout3D to generate a .stl file. I have:

first = ContourPlot3D[
  z Sin[Pi x] == -((Sqrt[44 + y^2] - y) x^2 + y) Cos[Pi x], {x, 0, 
   1}, {y, -10, 10}, {z, -150, 150}, Method -> {"Extrusion" -> .05}]

second = ContourPlot3D[-z Sin[
     Pi x] == -((Sqrt[44 + y^2] + y) x^2 - y) Cos[Pi x], {x, -1, 
   0}, {y, -10, 10}, {z, -150, 150}, Method -> {"Extrusion" -> .05}]

Then I just use Show and Printout3D:

combined = Show[first, second, PlotRange -> All]
 
Printout3D[combined, "combined.stl"]

It loads for 20 minutes and then produces the error:

"Printout3D : A correctly specified region expected at position 1 of Printout3D".

At first I thought the error had to do with differing x-domains but I made some tweaks and I got the same error. How can I specify a region at Position 1.

Thanks for any help!