When using statically configured webhooks, a racecondition occurs when hookshot is started and the connection validator checks whether the quickjs engine has been loaded: https://github.com/matrix-org/matrix-hookshot/blob/main/src/generic/WebhookTransformer.ts#L45-L47

It seems that the engine is only initialized after the config has been loaded: https://github.com/matrix-org/matrix-hookshot/blob/main/src/App/BridgeApp.ts#L51-L53