There’s definetely something up at the config level AFAICT, because I’ve dug into the code at the release level, and can see that the thing returning the 404 code is that standard, built-in http proxy (as in we’re not doing anything fancy to the request).
Which means that TIB really does think it’s getting a 404 back, not a 200, even though the request is arriving.
Are these docker containers? Can you curl from within the TIB container to your IDP?