Random value inside blueprint?

Hello,

I created a blueprint with a boolean called DoRandomizeValue (generate a random float). If i set the bool to true it generates a random float. After that the bool reset to false. That works all perfectly when i add the blueprint actor directly to the scene. But when i set the bool inside the blueprint to true under class defaults tab the construction script dont reset it to false again.

Is that a limit of blueprint actors? Is there a workaround to generate once random values inside a blueprint?

Greets