Why /VAADIN/push is considered as static resource (in 24.2.5) ?

I am experiencing the following error in production mode. It looks like /VAADIN/push is considered as static resource … Why? How can I overcome this warning? I don’t remember such a problems in the earlier versions …
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Error on page open/close in the latest version

Error on page open/close in 24.2.5

Why /VAADIN/push is considered as static resource (in 24.2.5) ?