Builders fail to finish buildings, just keep playing animation

[WhiteTreePaladin]

The units get stuck trying to build and sit there playing the animation, but the building sits at zero. It never gets built, so I don't think it is an issue with the GUI updating.

When re-tasked, they do start building again. It seems to never be the first thing they build, but rather happens when they finish a structure and move on to another automatically.

Attached are logs. It happened during the last build palisade command. (The command involved building some palisades that had been placed earlier.

logs.zip

Here's some images (the log does not apply to these pictures.)

[historic_bruno]

In the screenshots it appears there are units trapped in the foundation, and the building can't begin until they have cleared off. Can you confirm that?

[Ykkrosh]

The most useful screenshot would probably be with the camera looking vertically downwards, with obstruction overlay enabled.

I guess the problem is that you've got so many builders that one is standing inside the foundation (preventing the builders from making progress), and is completely surrounded by other units and is therefore unable to get out. I have no idea how we can avoid that problem, without letting units push each other out of the way so they'll never be permanently stuck when surrounded.