[4.7.2] Editor Crashes on Converted Project With Instanced Static Meshes

Thank you. I haven’t converted my project in place, it has always been as a copy. So I still have the original 4.6.1 version as I’m aware of this - I am purely doing this for testing new features / reporting bugs.

I’m glad to hear it, I just wanted to be sure. :slight_smile:

Hi Kenomica,

I attempted to reproduce this with some of my older projects that have been converted multiple times but without luck. So this seem to be confined to your main project and it could be caused by the general instability of the Preview build.

Preview 7 will be out soon. Once it is you could try retesting your project then.

If it still crashes, would you be willing to send me your project? If I can get a repro internally I can then make a report. If you are comfortable with that, you could send it by private message over the Forums.



Yeah, this project has been converted from every iteration since 4.1.

I will certainly try preview 7 when released, and if it’s still crashing I’ll send you a portion of the project.

I think if I were to send the full thing you’d be waiting until 4.9, my net is that slow haha.

Thanks for the support.

I gave Preview 7 a try - and almost the same thing happened - however this time it reaches 95% before the crash occurs, and even better - a callstack was generated!


Anything extra is good. Could you post the Log and Dmp files that generated with the new crash?

Sadly I no longer get a callstack or a DMP file. It seems it hard crashes before having the chance to generate either.

The callstack only appeared the first time after installing preview 7 (and I’ve tried multiple times since then by deleting the cloned project and trying again)

Even the log file seems incomplete, but here it is : LOG

I will uninstall and reinstall 4.7 Preview 7 in the hopes I can get a DMP file

Same exact behaviour in preview 8

Hi Kenomica,

I’m sorry that it’s been a few days. I have entered this as JIRA UE-10157 in our tracking software and our developers will be investigating the issue further.

We will post back here as soon as we have an update.



Is it possible you are using content from an old sample? There are some known issues with opening very old assets with 4.7, please see this post:

I’m pretty sure I’m not, but I’ll certainly give those fixes a try, thank you.

Gave it a try with the RC of 4.7 - exact same situation.

though I have a callstack, log and DMP to show which will hopefully help.


Log and DMP

I used the Command Prompt to re-save everything and sadly it didn’t solve the crash.

Happens still with 4.7.1

Do you have any blueprints in your map with instanced static mesh components that you are populating(/instancing) from construction scripts? Try deleting those and see if it helps.

I have the exact same issue as you and my testing showed such actors to be the root cause. See this forum post for more details.

Replied on the forum too, thank you. I’ll give that a try, since all my maps are generated with instanced static meshes.

I have updated the original question with more information after some users on the forum found what could be the cause.

Hi. can someone from Epic comment if there’s already a UE JIRA logged for this?

This is a pretty major issue IMO as it effectively prevents any use of static instanced meshes in a map.

Also, to add to Kenomica’s reproduction steps I want to clarify that the issue manifests only if lighting has been built. i.e. if you spawn instanced static meshes in your construction script but do not build lighting your level will load fine in 4.7. However, once you build lighting you will no longer be able to open the map the again.

I suspect InstancedStaticMeshComponentInstanceData/FLightMapInstanceData related code in InstancedStaticMesh.cpp is causing this crash (although admittedly I’m not familiar enough with these engine classes to be sure)


I entered JIRA UE-10157 for this issue but we haven’t been able to reproduce this in-house. I will try to see if I can get a repro with your additional steps. If I’m unable to, would you be willing to send a stripped down test project that has the issue?

Hi TJ Ballard, the project which I shared with you for an unrelated bug during 4.7 preview should also come handy in reproducing this You just need to turn ‘Force Precomputed lighting’ off in that level, build lighting once and try to restart the editor. In fact I had disabled lighting back then to circumvent this very issue.

Let me know if that doesn’t work out in which case I’ll try preparing a repro project.