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Wrong fix, I think.
\r\n is the specified line termination character in SDP, \n is exceptionally (but universally) accepted.
@fippo should look at this - either the pattern leaves a blank line (just the \r\n or \n), or it eats the \n when there's no \r and doesn't eat it when it's present.
I think you need extra regex modifiers to get substitutes to work past linebreaks (of any type).

The code takes loopbackAnswer as wssMessage.msg which is the serialized JSON which escapes all the SDP crlfs as \r\n. That is a bit silly and unexpected...
And yes, the pattern leaves blank lines, thank you! #667 should fix both

Thanks Philipp!