The only signal that can make it is the "it's ok to collapse" signal.
This "signal" is the fact that it was observed.
There is an alternative interpretation and I'm not 100% we ever actually refuted it, since the mechanism to refute it is pushing the limits of electrical switching capability but...
The alternative interpretation of EPR is that the state for each particle was set at creation.
Imagine you have two suitcases and a single pair of gloves, a left hand and a right hand glove.
You blindfold yourself and using tongs you pick up one glove and stick it in the suitcase on your right and another glove and stick it in a suitcase on your left.
Now you randomly mail the suitcases, one goes to bob in Hawaii and the other goes to alice in Antarctica.
No matter who opens which case, when. As soon as one case is opened the contents of the other is immediately known.
This was refuted in the mid 1970s, but the equipment to refute it was barely able to perform electrical switching at the requisite frequency. I have to admit, I haven't seen any new tests of bells theorem in the last decade or so.
I'll be honest with you. My instincts tell me the "mailed glove" scenario seems more likely. Which means that anything which proceeds from the bell's inequality test is suspect and should be repeated with more modern equipment and in a room that is better shielded from cosmic rays.
I think Susskind feels a little hesitance here too. He keeps saying "if ER=EPR" then...
RE: We might have already discovered wormholes and a new paper provides a way to use them?!