Our site is using Discourse 1.5.1 and I believe our hosting provider upgraded us from 1.4 last week. I have no control over this.
It appears that all API responses from Discourse have the content-type of "application/json". But I have found that under 1.5 when you issue PUT requests to Suspend an account it now responses with the content-type "text/plain".
I looked at a number of other PUT requests and they all were using "application/json" so I suspect this was an unintended change.
I'm using the pydiscourse library and until the upgrade didn't throw any errors for PUT requests. Now every PUT request generates an exception because the library checks the response content-type.
Please let me know if I can provide any additional detail.