Expression failed during Html5 launch

Hey,
i have a problem where i launch my project as Html5 in Firefox 64 bit and i get this alert message it opens my browser:

Expression (ImportPackage || FLinkerLoad::IsKnownMissingPackage(Import.ObjectName)) failed in D:\Build\++UE4+Release-4.16+Compile\Sync\Engine\Source\Runtime\CoreUObject\Private\Serialization\AsyncLoading.cpp:2163!
Check console for details.

Did one of you guys had this problem too and maybe can give me a hint how to solve it?

This looks like a new one. Any chance you’d be able to reduce the issue down to a specific part of the project in question that would cause it? Does it occur on all projects?

I actually only get this error if i add a new actor component to my project. Even if it is an empty component, i can not start my project again in html5. As soon as i remove it, i can launch it again.

Are you talking about child actor component or some other component?

I’m talking about the Components/ActorComponent you can add with “New C++ Class” in the Unreal Engine.