We are trying to use an external LTI tool - GoReact - and they are saying the lis_result_sourcedid is coming back as JSON and it shouldn't be. It was working in previous versions of Moodle (thought they won't tell me what versions), but they confirm it doesn't work now.
Here is their response:
We're seeing the same thing in our Moodle environment as well where it worked correctly before, so Moodle has changed something that is breaking grade passback. We'll have our developers take a look to see if there is anything that can be done on our end to work around the issue, but generally speaking we don't make changes to accommodate breaks from LTI specifications, if that's what is happening here. If you could also contact Moodle and let them know that LTI grade passback is failing that would be helpful.
Our initial suspicion is that it could be related to the hash value being passed, but that's just from a cursory investigation, so we don't have a high degree of certainty yet. Here's a sample payload segment with the hash if it helps Moodle when you reach out to them: