Engine Error "setup item rendering"

Summary: Tasks have included building moat around central town area. No builds build expect a stone bridge. Been mining down to bedrock. 10 Hearthlings, 1 Carpenter, 1 Farmer
Day 8 Dewmun. Error in image came up as a save was loaded. Proceeded to give the error until it reach 3378 of them and then stopped. Ran very choppy for a minute and then locked up.
Steps to reproduce:

Run a game for a bit (Maybe an hour or so), then save, quit and reload a few times. I played this file for a few hours, saving a reloading when the blue lau scipt would start dominating the process bar down at the bottom.

Expected Results: Close the error and continue playing.

Actual Results: Error continued util game crash.

Versions and Mods: A11 develop 453

System Information:

Windows 7 x64
12GB DDR3 RAM
Intel Core i7-3610QM, 2.3GHz
Primary graphics processor: Nvidia GT670M w/ 3 GB RAM

Files include: Picture of error, stoneheath log.

The log turned out to be incredibly large (32.8 MB), so I’ll just post the part that seemed to be repeating itself. I have saved it in case it needs to be referenced.

2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | – Script Error (lua) Begin -------------------------------
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | stonehearth/ai/observers/aggro_observer.luac:6: attempt to index local ‘sensor_list’ (a nil value)
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | stack traceback:
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | radiant/modules/events.luac:68: in function <radiant/modules/events.luac:65>
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | stonehearth/ai/observers/aggro_observer.luac:6: in function '_add_sensor_trace’
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | stonehearth/ai/observers/aggro_observer.luac:4: in function 'obj’
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | radiant/modules/events.luac:15: in function 'self’
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | radiant/modules/events.luac:80: in function <radiant/modules/events.luac:78>
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | [C]: in function 'xpcall’
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | radiant/modules/events.luac:78: in function 'trigger’
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | radiant/modules/events.luac:97: in function '_update’
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | radiant/server.luac:19: in function <radiant/server.luac:17>
2015-Oct-03 15:37:55.511457 | server | 0 | lua.code | – Lua Error End -------------------------------