OK so looking at that log it seems to me that their LMS is removing the quotes from the 'suspend_data', which makes it invalid.

According to those logs, the data being returned to the course from the LMS is:

{assessment:{ChapterOneEpilogue_Q1:[0,0,null,0,1,{58ab15ec1df44d210672d6ec:true,58ab160c1df44d210672d6ee:null}]},completion:-10,questions:CIhOiBYQBEA4MfCgi,_isCourseComplete:false,_isAssessmentPassed:false}

But it should be like this:

{"assessment":{"ChapterOneEpilogue_Q1":[0,0,null,0,1,{"58ab15ec1df44d210672d6ec":true,"58ab160c1df44d210672d6ee":null}]},"completion":-10,"questions":"CIhOiBYQBEA4MfCgi","_isCourseComplete":false,"_isAssessmentPassed":false}

Try putting either of those into a JSON validator and you'll see that the first is full of errors but the second is error-free.

You should go back to the people who control the LMS and explain this to them. They should not be changing the suspend_data format - JSON is perfectly valid.

Hope this helps.