ENDPOINT_MESSAGE_RECEIVED is triggered two times

I updated from 5675 and after that I noticed that messages via sendEndpointMessage are sent twice.

To reproduce:
window.APP.conference.sendEndpointMessage("",1321231) via dev console

add
console.log(action) to line 54 in
/react/features/subtitles/middleware.js (or any other middleware which handles endpoint messages

As you can see, the sendEndpointMessage with 1321231 as payload is received 2 times on the right side. The other endpoint messages are from “e2e-ping-request”.
Happens with Chrome and Firefox.

This is what I get with the old version

If important:
I tested it with version 2.0.7001 and 2.0.6865-2.
Webpage is served via webpack.