Airfoil Error Log:
RTSP Protocol Error
Could not parse response from remote speaker
Please include the following information when contacting Rogue Amoeba Support.
Domain: SSAirfoilErrorDomain
Code: -1500
NSLocalizedDescription: RTSP Protocol Error
NSLocalizedRecoverySuggestion: Could not parse response from remote speaker
SSHTTPStatusCodeKey: -1
SSRTSPRequest: ANNOUNCE rtsp://192.168.0.92/3462004426 RTSP/1.0
Active-Remote: 3143294795
Client-Instance: 75D9DF9D52B1E4F4
Client-instance-identifier: 236A0B50-DC32-44A3-961F-41815DFA5F90
Content-Type: application/sdp
CSeq: 1
Content-Length: 571
User-Agent: Airfoil/4.8.0 (Macintosh; N; Intel)
Client-computer-name: Dean's_Macbook_Pro
DACP-ID: 14049CD74C6B23B7
v=0
o=iTunes 3462004426 0 IN IP4 192.168.0.92
s=iTunes
c=IN IP4 192.168.0.9
t=0 0
m=audio 0 RTP/AVP 96
a=rtpmap:96 AppleLossless
a=fmtp:96 352 0 16 40 10 14 2 255 0 0 44100
a=rsaaeskey:Gr8qH5+zsUtaMxUYMMgoZQbqt06ALtW7FD916WSnEBW8mRNypyRO13a4D5bUaVH2HOcYHYNO49jAn6zmIJo4IpdqBAkVXqLfSQAU3WlPJxleLJhNtMJv/yn0v8gD6lFBZhhDhxgHyUCrYbI63SZhSoZv8aiFyh/RE1XQFmDsbt/QzkjIWy5zXbkPNX227UP7/b1s9gwRbPYVmD29fyt3cjhJageU64hTDAOYgECQ6TCo9zQMoRTNQzdQLpcxfoDLctGuBZExByyoBEkroh0cD+JQFKrO1aPf5g9HWF9Gqo0cGrrb9JknPjYPoI0Rr3uegjU717+R1WippeQJiIporw
a=aesiv:AAECAwQFBgcICQoLDA0ODw
SSRTSPResponse: Apple-Response: VGQ+6s3WDSb3TI/q97kUBTdSpwktqtBMPX/1xtHmEWgGTZkS3gsomCRT/MJxTBBYVztyuSmuMyePfKvlj2NqlPchUKhsRNMV1HoKQb5XK0baIuQOuaFSSoTXfMaHCoyL7vLQFPeBHXpSIvgro7pUvqydMuHGqsv0myJVpSRjThX5ynW4OUOtt11Yrs/QO99Iu8gWN3p2aktEXWcCvJEZZ1gWCRIkWnkAaVb/RnTuc1ix+XWh5rA6qYsS38QxP6vmSAFwtvjZlrwtWcra+Z1UHQ8j8XXN4KXgNeK+l/N3JX5tmSTqWXPt1/kdOnh8H3X1iKOpM86R6Uji2Tsrv1pNgA
CSeq: 1
Audio-Jack-Status: connected; type=analog
Public: ANNOUNCE, SETUP, RECORD, PAUSE, FLUSH, TEARDOWN, OPTIONS, GET_PARAMETER, SET_PARAMETER

Quote from another forum:
"(…)Under some circumstances, RTSP responses would be split into multiple
packets. This causes Airfoil to barf, as it interprets the end of the
packet as the end of the response. Since TCP_CORK is not portable, this
fix buffers the packet on the stack before using a single write.(…)"