when parsing decl files, you can fail to specify correct assets or non-existing assets, in that case the engine tries to open it and, in not finding them, it tries to open a default option.
This usually fails with the following message:

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ERROR: Attempted to load material decl 'lights/defaultpointlight' from game thread!

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the asset itself exists, but it wasn't compiled for that entity, it wasn't parsed before the game code calls it, so the engine fails, it could be wise to round up a core set of assets an force the engine to parse them so when the engine calls for them they are already there ( it usually happen with lights ), in case of not finding those core assets then the engine should fail.

this issue is very tough on the developer, because the announced error message doesn't have anything in common with the actual wrong doing in the decl that eventually prompted the error message.