# Engine crashes when building lighting (engine version 4.12.4)

**URL:** <https://forums.unrealengine.com/t/engine-crashes-when-building-lighting-engine-version-4-12-4/362946>\
**Category:** Platform & Builds\
**Tags:** crashes, build, unreal-engine, bug-report, UE4, question\
**Created:** [July 4, 2016, 11:31pm UTC](https://forums.unrealengine.com/t/engine-crashes-when-building-lighting-engine-version-4-12-4/362946 "2016-07-04T23:31:05Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![Tim\_Hobson](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Tim\_Hobson](https://forums.unrealengine.com/u/Tim_Hobson)\
**Post date:** [July 5, 2016, 6:13pm UTC](https://forums.unrealengine.com/t/engine-crashes-when-building-lighting-engine-version-4-12-4/362946/6 "2016-07-05T18:13:54Z")

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Retrieve the super verbose logs from Swarm Agent following instructions in this page.

Swarm should not cause the editor to crash since it’s a separate program that handles the building process.

You may also want to follow notes in this page to see if Swarm is using the right ports. If not, you’ll want to correct this on your machine since this is not an issue with UE4 or Swarm but your machine and the ports that are free.

> **[Does UE4 / Swarm Require a "D" Drive?](https://forums.unrealengine.com/questions/363295/does-ue4-swarm-require-a-d-drive.html)**
>
> Hello, I am currently experiencing issues with building lighting. When I initiate a build, Unreal gets stuck at “Gathering Scene Geometry” I looked toward the Swarm Agent and discovered this error in the log: 2:25:20 PM: \[ERROR\] Channel...

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