I actually had to solve the same issue recently, in my case it was in between 2 google drive APIs.
The main issue was caused by the binary input view from the HTTP Client which expects lower case $['content-location'] and $['content-type']. You can use a mapper in between the two to solve this problem, this should solve this for now, while we work to enhance this behaviour so that the HTTP Client Input view support all case variations of the Content* headers.