# Navigation randomly skips HISM instances **URL:** \ **Category:** AI\ **Tags:** Hierarchical-Instanced-Static-Mesh, navigation-mesh, Navigation, dynamic-navmesh, unreal-engine, question\ **Created:** [August 16, 2017, 7:50pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742 "2017-08-16T19:50:33Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![lotodore](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@lotodore](https://forums.unrealengine.com/u/lotodore)\ **Post date:** [August 16, 2017, 7:50pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/1 "2017-08-16T19:50:33Z")
After [Unreal Engine Issues and Bug Tracker (UE-48309)](https://issues.unrealengine.com/issue/UE-48309) was fixed, I still have trouble with HISM. The navigation considered HISM instances fine in UE 4.16.3, but is completely broken for my project in UE 4.17.1. A line of dynamically spawned instances looks like this in 4.16.3 (with console command “show Navigation” and dynamic navigation enabled): ![204481-navigation_4_16_3.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/8/4/0/840a196d2950815c7e2903f6b6c2b31349c96bb9.png) The same level in 4.17.1 looks like this: ![204482-navigation_4_17_1.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/1/a/d/1ad3dc7e4b9f3a29c5f1684e836e8e827eaf73ac.png) As you see, it randomly connects instances, even though all instances have the same BP class. Is this a known bug? Do I need to wait for 4.18 to use dynamically created HISM again? Edit: All instances have the same Z position, so the reason cannot be one instance being smaller/above ground/whatever. Also, the result stays the same if I adjust the Z value. HISM also has “can character step on it” set to false. ---
**Author:** ![lotodore](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@lotodore](https://forums.unrealengine.com/u/lotodore)\ **Post date:** [August 16, 2017, 9:25pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/2 "2017-08-16T21:25:27Z")
I deleted everything from my game project in order to provide a minimal project to reproduce the issue. See the attached zip file. [minimal project][1] If you open this project with UE 4.17.1, run the game, fly around a bit for top down view, and “show Navigation” in the console, it will show the following picture: ![204487-navigation_bug.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/9/289bdfa71c5ce5e1f24b9abb5ec2adac86b4c19f.png) Also note that I keep getting “save failed” errors with this simple map in 4.17.1, maybe this is related. ---
**Author:** ![anonymous\_user\_565e242f](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_565e242f](https://forums.unrealengine.com/u/anonymous_user_565e242f)\ **Post date:** [August 29, 2017, 11:57am UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/3 "2017-08-29T11:57:15Z")
Hi I’m currently looking at your issue, and hopefully it will make it in 4.17.2, will let you know. ---
**Author:** ![anonymous\_user\_565e242f](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_565e242f](https://forums.unrealengine.com/u/anonymous_user_565e242f)\ **Post date:** [August 30, 2017, 6:24pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/4 "2017-08-30T18:24:15Z")
A fix was made and will be available for 4.17.2 ---
**Author:** ![lotodore](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@lotodore](https://forums.unrealengine.com/u/lotodore)\ **Post date:** [August 31, 2017, 10:02pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/5 "2017-08-31T22:02:47Z")
This is great news, thank you very much. ---
**Author:** ![lotodore](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@lotodore](https://forums.unrealengine.com/u/lotodore)\ **Post date:** [September 26, 2017, 6:04pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/6 "2017-09-26T18:04:46Z")
I had to skip 4.17 due to [Unreal Engine Issues and Bug Tracker (UE-48361)](https://issues.unrealengine.com/issue/UE-48361) I just tested using 4.18 preview 2 and navigation is still broken with HISM instances for my project. The above minimal project works fine, however, so I’m afraid I have no small project to reproduce. Is this still a known issue in 4.18? I somehow fear I’ll be stuck with 4.16 forever or required to use individual actors. This screenshot is from 4.18 preview 2: ![214808-navigation-4-18-preview2.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/1/5/4/154bfe6e3ba524a33135f0e1cecb86f2c5f88222.png) ---
**Author:** ![anonymous\_user\_565e242f](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_565e242f](https://forums.unrealengine.com/u/anonymous_user_565e242f)\ **Post date:** [September 26, 2017, 6:36pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/7 "2017-09-26T18:36:18Z")
Well technically, the bug was fixed ans submitted in 4.17.2, i’ll check to be sure i bring the change back for 4.18 and will let you know. ---
**Author:** ![anonymous\_user\_565e242f](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_565e242f](https://forums.unrealengine.com/u/anonymous_user_565e242f)\ **Post date:** [September 26, 2017, 6:49pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/8 "2017-09-26T18:49:12Z")
So i confirm it was bring back, but i checked in yesterday, so it will be available in the next preview of 4.18 i guess. ---
**Author:** ![lotodore](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@lotodore](https://forums.unrealengine.com/u/lotodore)\ **Post date:** [October 4, 2017, 8:31pm UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/9 "2017-10-04T20:31:43Z")
Thanks, the navigation is fixed for me in 4.18 preview 3! However, HISM is still broken for me compared to 4.16.3 - please see bug report [https://answers.unrealengine.com/questions/712662/multiboxtraceforobjects-sometimes-returns-the-same.html](https://answers.unrealengine.com/questions/712662/multiboxtraceforobjects-sometimes-returns-the-same.html) . I guess I just use HISM for too much stuff :-(. So far I failed to reproduce this in a small project, if you need this I will try this weekend. ---
**Author:** ![anonymous\_user\_565e242f](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_565e242f](https://forums.unrealengine.com/u/anonymous_user_565e242f)\ **Post date:** [October 5, 2017, 11:16am UTC](https://forums.unrealengine.com/t/navigation-randomly-skips-hism-instances/401742/10 "2017-10-05T11:16:49Z")
Glad to hear your issue is fixed, however for the other one, yes i would need a good repro or ideally a test project to properly investigate what is happening. Thanks!