Inherited component properties on actor instances of derived blueprints are silently reset to defaults when the blueprint enters a compile error state and is subsequently fixed

When an instance of a child blueprint in a level enters the “Bad Blueprint” state due to a compile error it will reset to default values when it is restored after the compile error has been fixed.

See repro steps and the linked EPS issue for details.

1. Create blueprint BP_Test of Actor class.
   1. Create function Test in BP_Test
   2. Add a boolean input parameter to the Test function.
   3. Add mesh component to BP_Test, do not set a mesh_._
2. Create BP_Test_Child as child blueprint class of BP_Test.
   1. Call Test function in BP_Test_Child, pass a variable into the call.
   2. Place BP_Test_Child in your level and change the mesh on the static mesh component.
3. In BP_Test function Test delete the boolean parameter in the Test function and save and compile it. This causes a compile error in the BP_Child Blueprint.
   1. Fix error caused by previous step in BP_Test_Child, e.g. by disconnecting connected variable to now invalid input and save and compile.
   2. Observe that BP_Test_Child placed in level has been set to the default values and the mesh is no longer overridden (applies to any changes to data for the instance in the level)

Pre-broken:

!

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-20260306-165415.png"!

After trying to recompile BP_Test_Child:

!

{5CED679D-3746-4828-8798-BE0E116CAEAA}-20260306-165448.png|width=411,alt="{5CED679D-3746-4828-8798-BE0E116CAEAA}

-20260306-165448.png"!

After compilation is fixed and child recompiled again:

!

{93F0C094-2395-42BC-B012-C209A9F3ED2B}-20260306-165554.png|width=380,alt="{93F0C094-2395-42BC-B012-C209A9F3ED2B}

-20260306-165554.png"!