It seems we are picky about conformance to NTRIP V2, maybe the caster you use is NTRIP V1? The content-type was different in NTRIP V1. There are also other differences with NTRIP V1 that made it impossible to parse with regular HTTP handling, the major one being that instead of using “HTTP/1.1 200 OK” as the first response line, NTRIP V1 used “SOURCETABLE 200 OK”, which broke everything!
Do you have a correct first line and only an incorrect content-type (hence some hybrid between NTRIP V1 and NTRIP V2)?