One of key security features of ZRTP encrypted phone calls - key continuity - has been removed from RedPhone when it has been integrated into Signal. See this issue for more info:

#4226: No warning when getting a call from contact with new key

Moxie closed it without explanation why it has been removed (with simple "yes you have to verify the sas every time").

Would you agree to reimplement it (well, it seems to be only commented out in the code, so it shouldn't be that hard) in your WebSocket fork? I can look into it when I get time if you are interested in it.