# Using 'Does Path Exist' decorator with dynamic nav mesh rebuild in v4.8 crashes game **URL:** \ **Category:** AI\ **Tags:** Behavior-Tree, unreal-engine, path, navmesh, bug-report, question\ **Created:** [June 11, 2015, 5:53pm UTC](https://forums.unrealengine.com/t/using-does-path-exist-decorator-with-dynamic-nav-mesh-rebuild-in-v4-8-crashes-game/321431 "2015-06-11T17:53:46Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Stormrage256](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/stormrage256/32/1008648_2.png) [@Stormrage256](https://forums.unrealengine.com/u/Stormrage256)\ **Post date:** [June 11, 2015, 5:53pm UTC](https://forums.unrealengine.com/t/using-does-path-exist-decorator-with-dynamic-nav-mesh-rebuild-in-v4-8-crashes-game/321431/1 "2015-06-11T17:53:46Z")
Hi, I’m using a Behavior Tree which determines if a path exists between two vectors. Run time nav rebuild is also enabled in my project. Everything was working fine in v4.7. However when I converted the project to v4.8, it started crashing at game launch. After going through the code, I realized that the ‘Does Path Exist’ when combined with dynamic nav mesh generation in v4.8 is causing it to crash. In order to rule out the possibility of corruption during conversion, I created a new first person project in v4.8 with just this test case. And the game started crashing again. It doesn’t occur when nav mesh generation is static or using nav mesh modifier. Only when it’s dynamic. As for the vectors, I’ve used them as the default values as well as the their values after projecting them to navigation. In both cases, the project crashes. If you guys want the project files or log files, I can provide them. ---
**Author:** ![TJ\_V](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/tj_v/32/1008648_2.png) [@TJ\_V](https://forums.unrealengine.com/u/TJ_V)\ **Post date:** [June 11, 2015, 7:06pm UTC](https://forums.unrealengine.com/t/using-does-path-exist-decorator-with-dynamic-nav-mesh-rebuild-in-v4-8-crashes-game/321431/2 "2015-06-11T19:06:59Z")
Hi Stormrage256, Yeah, if you could provide the test project that you created that would be helpful. Also, the crash reporter Callstack, Log, and DMP files could also be useful. ---
**Author:** ![Stormrage256](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/stormrage256/32/1008648_2.png) [@Stormrage256](https://forums.unrealengine.com/u/Stormrage256)\ **Post date:** [June 11, 2015, 8:07pm UTC](https://forums.unrealengine.com/t/using-does-path-exist-decorator-with-dynamic-nav-mesh-rebuild-in-v4-8-crashes-game/321431/3 "2015-06-11T20:07:57Z")
Hi TJ, Here’s a dropbox link to the bug reproduced in First Person template: [DropBox: UE4.8 Project](https://www.dropbox.com/s/4paf41x35tnzs60/MyProject3%204.8.zip?dl=0) All the save and log files are included in it. I’ve also attached text files containing crash report data in two cases: CrashReport CrashReport2 ---
**Author:** ![TJ\_V](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/tj_v/32/1008648_2.png) [@TJ\_V](https://forums.unrealengine.com/u/TJ_V)\ **Post date:** [June 16, 2015, 6:20pm UTC](https://forums.unrealengine.com/t/using-does-path-exist-decorator-with-dynamic-nav-mesh-rebuild-in-v4-8-crashes-game/321431/4 "2015-06-16T18:20:38Z")
Hi Stormrage256, Sorry it’s been a few days and thank you for all of the additional info. It helped me reproduce the issue in our latest internal build so I created JIRA UE-17141 in our tracking software. Our developers will be investigating the issue and we will post back here with updates as we have them. As for a workaround, I haven’t found anything reliable. I noticed if the ‘Does Path Exist’ is deleted and replaced in your test project, then it doesn’t crash. However, the reason it doesn’t crash is because the event stops succeeding. I changed it to check the distance between the Spawn \> Core and it still crashes. Cheers, TJ ---
**Author:** ![Stormrage256](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/stormrage256/32/1008648_2.png) [@Stormrage256](https://forums.unrealengine.com/u/Stormrage256)\ **Post date:** [June 25, 2015, 3:18am UTC](https://forums.unrealengine.com/t/using-does-path-exist-decorator-with-dynamic-nav-mesh-rebuild-in-v4-8-crashes-game/321431/5 "2015-06-25T03:18:51Z")
Hi TJ, do you know if a fix for this issue would be available in the 4.8.2 version? ---
**Author:** ![TJ\_V](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/tj_v/32/1008648_2.png) [@TJ\_V](https://forums.unrealengine.com/u/TJ_V)\ **Post date:** [June 25, 2015, 2:21pm UTC](https://forums.unrealengine.com/t/using-does-path-exist-decorator-with-dynamic-nav-mesh-rebuild-in-v4-8-crashes-game/321431/6 "2015-06-25T14:21:59Z")
Hi Stormrage256, Hotfix builds are generally reserved for widespread showstopping bugs and at this point it hasn’t been determined if a 4.8.2 build will even be released. The fix for this issue is currently set to be included in 4.9.