Add new comment on issue not setting comment text

we have been using the APIs for comment on issue, push and pull request. the content parameter is set as application\json payload, which used to work fine for all three, but from yesterday we are seeing that this is not setting the comment text for issues. On sending the content as url encoded form parameter i was able to resolve the issue.

Was there a change to move to url encoded param? I dont see anything specific in the documentation..