# Engine Error while building tower portion of building

**URL:** <https://discourse.stonehearth.net/t/engine-error-while-building-tower-portion-of-building/27732>\
**Category:** Bug Reports\
**Tags:** building, a19r687\
**Created:** [January 12, 2017, 9:39pm UTC](https://discourse.stonehearth.net/t/engine-error-while-building-tower-portion-of-building/27732 "2017-01-12T21:39:02Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Rakeesh](https://sea2.discourse-cdn.com/flex022/user_avatar/discourse.stonehearth.net/rakeesh/32/40291_2.png) [@Rakeesh](https://discourse.stonehearth.net/u/Rakeesh)\
**Post date:** [January 12, 2017, 9:39pm UTC](https://discourse.stonehearth.net/t/engine-error-while-building-tower-portion-of-building/27732/1 "2017-01-12T21:39:03Z")

</div>

**Summary:** Engine error pop-up during construction of a tower portion of a building. Tower does not contain any entries except the roof space used for construction.

**Notes:**  
release-687 (x64)  
…/services/server/build/ladder\_builder\_destructor.lua:44: attempt to call method ‘get\_num\_handles’ (a nil value)  
stack traceback:  
radiant/modules/common.lua:237: in function ‘report\_traceback’  
radiant/modules/common.lua:248: in function ‘get\_num\_handles’  
…/services/server/build/ladder\_builder\_destructor.lua:44: in function ‘is\_last\_handle’  
stonehearth/components/scaffolding/scaffolding.lua:558: in function ‘destroy\_handles’  
stonehearth/components/scaffolding/scaffolding.lua:634: in function ‘\_update\_ladders’  
stonehearth/components/scaffolding/scaffolding.lua:310: in function ‘recalculate\_scaffolding\_blueprint’  
…hearth/services/server/build/scaffolding\_manager.lua:289: in function ‘\_process\_changes’  
…hearth/services/server/build/scaffolding\_manager.lua:279: in function ‘obj’  
radiant/modules/events.lua:83: in function ‘instance’  
radiant/modules/events.lua:291: in function \<radiant/modules/events.lua:285\>  
[C]: in function ‘xpcall’  
radiant/modules/common.lua:257: in function ‘xpcall’  
radiant/modules/events.lua:285: in function ‘trigger’  
radiant/modules/events.lua:398: in function ‘\_trigger\_gameloop’  
radiant/modules/events.lua:446: in function ‘\_update’  
radiant/server.lua:61: in function \<radiant/server.lua:58\>

**Attachments:**

 ![](https://us1.discourse-cdn.com/flex022/uploads/stonehearth/original/3X/7/6/76833c529c95e9f33b639cafd75fb007da81d78b.jpg)

 ![](https://us1.discourse-cdn.com/flex022/uploads/stonehearth/original/3X/b/0/b06d6f15258c5b097341a8ef43ba27a9117e5b31.jpg)

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<div class="post-metadata">

**Author:** ![Rakeesh](https://sea2.discourse-cdn.com/flex022/user_avatar/discourse.stonehearth.net/rakeesh/32/40291_2.png) [@Rakeesh](https://discourse.stonehearth.net/u/Rakeesh)\
**Post date:** [January 12, 2017, 9:54pm UTC](https://discourse.stonehearth.net/t/engine-error-while-building-tower-portion-of-building/27732/2 "2017-01-12T21:54:37Z")

</div>

**Update:**  
Construction has halted on the building, leaving one side of the tower incomplete to its floor and not putting on its roof.

Save/load produces no error message.

After left running for several minutes another Engine Error occurred:

**Notes:**  
release-687 (x64)  
stonehearth/ai/actions/patrol\_helpers.lua:55: attempt to index local ‘pathfinder\_component’ (a nil value)  
stack traceback:  
[C]: ?  
stonehearth/ai/actions/patrol\_helpers.lua:55: in function ‘get\_next\_path\_point’  
stonehearth/ai/actions/walk\_in\_formation\_action.lua:82: in function ‘\_get\_intercept\_speed’  
stonehearth/ai/actions/walk\_in\_formation\_action.lua:48: in function ‘\_changed\_cb’  
radiant/modules/filtered\_trace.lua:12: in function \<radiant/modules/filtered\_trace.lua:7\>

**Attachments**

 ![](https://us1.discourse-cdn.com/flex022/uploads/stonehearth/original/3X/3/b/3bf58064893d8faf2d449d0fdc7bad012d17afd2.jpg)1

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<div class="post-metadata">

**Author:** ![Rakeesh](https://sea2.discourse-cdn.com/flex022/user_avatar/discourse.stonehearth.net/rakeesh/32/40291_2.png) [@Rakeesh](https://discourse.stonehearth.net/u/Rakeesh)\
**Post date:** [January 12, 2017, 9:59pm UTC](https://discourse.stonehearth.net/t/engine-error-while-building-tower-portion-of-building/27732/3 "2017-01-12T21:59:56Z")

</div>

**Update:**  
Destruction of building (to start construction over) results in 2 engine errors.

**Notes:**  
release-687 (x64)  
stonehearth/ai/actions/patrol\_helpers.lua:55: attempt to index local ‘pathfinder\_component’ (a nil value)  
stack traceback:  
[C]: ?  
stonehearth/ai/actions/patrol\_helpers.lua:55: in function ‘get\_next\_path\_point’  
stonehearth/ai/actions/walk\_in\_formation\_action.lua:82: in function ‘\_get\_intercept\_speed’  
stonehearth/ai/actions/walk\_in\_formation\_action.lua:48: in function ‘\_changed\_cb’  
radiant/modules/filtered\_trace.lua:12: in function \<radiant/modules/filtered\_trace.lua:7\>

release-687 (x64)  
…/services/server/build/ladder\_builder\_destructor.lua:44: attempt to call method ‘get\_num\_handles’ (a nil value)  
stack traceback:  
radiant/modules/common.lua:237: in function ‘report\_traceback’  
radiant/modules/common.lua:248: in function ‘get\_num\_handles’  
…/services/server/build/ladder\_builder\_destructor.lua:44: in function ‘is\_last\_handle’  
stonehearth/components/scaffolding/scaffolding.lua:185: in function ‘\_destroy\_immediately’  
stonehearth/components/scaffolding/scaffolding.lua:248: in function ‘\_on\_scaffolding\_destroy\_immediately’  
stonehearth/components/scaffolding/scaffolding.lua:147: in function ‘obj’  
radiant/modules/events.lua:83: in function ‘instance’  
radiant/modules/events.lua:291: in function \<radiant/modules/events.lua:285\>  
[C]: in function ‘xpcall’  
radiant/modules/common.lua:257: in function ‘xpcall’  
radiant/modules/events.lua:285: in function ‘trigger’  
…  
radiant/controllers/time\_tracker\_controller.lua:82: in function ‘set\_now’  
radiant/controllers/time\_tracker\_controller.lua:103: in function ‘increment\_now’  
radiant/modules/timer.lua:13: in function ‘instance’  
radiant/modules/events.lua:291: in function \<radiant/modules/events.lua:285\>  
[C]: in function ‘xpcall’  
radiant/modules/common.lua:257: in function ‘xpcall’  
radiant/modules/events.lua:285: in function ‘trigger’  
radiant/modules/events.lua:398: in function ‘\_trigger\_gameloop’  
radiant/modules/events.lua:446: in function ‘\_update’  
radiant/server.lua:61: in function \<radiant/server.lua:58\>

**Attachments: Building Template**  
[town hall.zip](https://discourse.stonehearth.net/uploads/short-url/2u4idDsVTSdDrruRUDhkHTCgIco.zip) (19.0 KB)