I have since been able to further isolate this crash issue.
It happens to meshes which are past a certain triangle count.
For example, (at least on my PC) a guaranteed way to make UE5 crash during project migration is to have a 4 Million+ triangles mesh in the UE4 project.
Interestingly enough, this happened both on my PC with 32GB RAM and one with 64GB.
I doubt it’s a hardware limitation, the crash seems to happen to everyone, past a certain triangles count of the UE4 mesh.
What’s the best way to report this issue to Epic right now?
I didn’t see any UE5 related issues on AnswerHub yesterday, at a quick glance.
I found a cumbersome workaround:
In your UE4 project, create an empty map and make it the default startup map for the game and the editor.
Now migrate the project to UE5, it will not crash anymore, because the map is empty and has not highpoly meshes in it.
In UE5 right-click on content browser folder that contains your static meshes, or just the Content folder of the project. → Audit Assets.
Sort the list by Exclusive Disk Size.
Start opening up static meshes with the highest disk size.
They’ll all crash the editor, because high disk size == high polycount.
As you go down the list, eventually no crash will occur once the polycount is low enough.
Now, at your own risk, delete the static meshes that caused the crash, when you opened them.
Then, (re-) import them into UE5. Curiously enough, importing the meshes directly into UE5 does not cause the crash. Now you can open your map, which used to have the deleted meshes.
If you had them placed in the map, you can now select the imported meshes to be used in place of the deleted ones again in the map.
PS: If anyone from Epic reads this, this workaround is NOT sustainable for us in the long run, since we’ll continue to develop in UE4 this year, but need to convert the project to UE5 every month, or so, to check performance, compatibility etc.
So using this workaround would easily cost our team 1000s of dollars worth of work-hours during 2021.