UE5 crashes when opening Character BP from UE5 Early Access with error TargetNumVerts >= LimitNumVerts

When trying to open anything that references our character BP (a gamemode, a map with said gamemode, another BP) coming from UE5 Early Access, the editor crashes with the following error:

Assertion failed: TargetNumVerts >= LimitNumVerts [File:D:\build++UE5\Sync\Engine\Source\Developer\MeshSimplifier\Private\MeshSimplify.cpp] [Line: 849]

We can’t even open the assets to debug the problem, or migrate them to a new project.

Does anyone know what might be causing this and how to solve it?

We discovered some meshes are making it crash as soon as they are loaded in memory, so loading anything referencing them even indirectly will make the editor crash with that error. We managed to isolate which meshes cause this but there is no apparent connection or difference from all the others. The error doesn’t happen if we re-download them from Megascans and import them anew.
They are all static meshes and not polygon heavy (definitely not enough to put Nanite to test or even UE4). Any idea?

I’m having the same exact problem as well haha. Did you figure out a fix?

We believe it’s the reduction setting for the LODs in the mesh editor. If the value is too low, it crashes the editor.

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If you created a static mesh within the editor itself, you can’t really do much to re-import anything. How would you change the LOD setting when even right-clicking the mesh in the content browser causes a crash?

No way to. You would need to change the settings before converting the project and then try again. Or just wait for a fix from Epic.

same here, need help!

Change what settings? What and where? The 3D asset causing these problems is a static mesh I made by combining two cubes together in Unreal Engine 5.

From our tests it should be Percent vertices under reduction settings. When it’s too low it crashes. But it could as well be something else or more than one thing causing it.

Related post:

I am having the exact same issue with the MeshSimplify.cpp. I can’t open any BluePrints after updating thanks to this error on line 849. Any fix??

Its already July 2022 and the problems has not been resolved by Unreal. My entire project is based on blueprints so I can’t even open them. They work fine in other projects but not in my main one. I just now submitted the ticket for this issue, I will let you know what they say. It was working fine in UE4.26 but not in UE5. Its frustrating to work around it. Almost impossible and puts entire project to a halt .

So I had the same issue, and as confirmed previously by @hale326 , it happenned to be an LOD problem indeed.
I duplicated and opened the project with its working version of Unreal (4.26) and deleted all the LODs I’ve configured on each assets manually to end up only with LOD 0 on them (maybe there is a command to automate the process or something instead…)
Then I was finally able to open the project in Unreal 5. Have to rework again on the assets’s LODs now =/
Hope that helps.