Summary:
I have a fence around my pasture. I laid out a freestanding wall adjacent to the fence. The workers chose to start building the wall on the same side as the fence. They completed the first course of stone. Then the worker went to construct the scaffolding to allow the second course to be laid. Except the worker could not complete the first scaffold block (same space as fence) and just showed the “working” animation for an extended period (until I removed the fence). The other side of the wall was open and could have supported scaffold just fine.
Reproduction:
- build a fence
- lay out (design) a wall adjacent to the fence. Click build.
- The worker may or may not decide to lay scaffold on the fence side.
Actual results:
If workers choose to construct scaffold on top of fence they will “work” forever without completing anything.
Notes:
This is more of an issue about worker decisions on creating scaffold. Items should not have scaffold laid on top of them. The worker should realize they cannot build scaffold in the space and look for alternatives… such as building the scaffold in a free space.
Workaround:
Dont put items where the workers need to work! Duh! 
Attachments:
This is the worker sitting in the fence building forever. A sheep decided to get in his way too but the sheep moved onto the space after he was already having difficulties.
Build:
Alpha 10.5
No mods
System:
Windows 8.1
Plenty of horsepower.
PS:
Great game, havent had any problems except above.