[Alpha 6] Change to roof material with pre-designed buildings breaks construction

Title

Bug: Changing roof texture on pre-designed buildings prevents construction of roof

Summary

When I build one of the pre-designed buildings but change the roof material from “wood” texture to one of the colours (yellow, blue, red), I get odd construction behaviour. Specifically, the walls get built, and then workers go idle.

Steps to Reproduce

  1. Place a pre-designed building
  2. Change the roof texture to something other than the default texture for the design
  3. Click “Build” to begin construction

Expected Results

Completed construction of building

Actual Results

Workers go idle after walls are constructed, and do not construct roof

Notes

If I return to the building menu once the workers go idle, click on the unconstructed roof blueprint, and click “Build!” again, the workers return and complete the roof. However, they do not remove the scaffolding at that point.

This bug is common to all the pre-designed buildings, but does not happen when I custom-design a building. It is common to all colours of roof other than natural wood, though I have not tested changing it, then changing back to brown before building.

It does not prevent me from designing and building other buildings - it only prevents me from using the ones that I build with changed roof textures.

Save/restart does not resolve the problem, nor does giving the workers another job to jostle them back into action - they finish their other job and then go back to idling.

I have not yet tested what happens on changing the wall texture; I will update on further testing.