@niallCIT20 You mentioned the images were pasted into the text box. If the student did a copy and paste of an image, either by using the keyboard shortcut Ctrl+P or right click to Paste, the image will not be saved in Canvas. I tested this and in the instructor grade book I did see (no answer) in the answer box for the question.
The correct way to insert an image is to go to the image icon in the toolbar, see below:
I have had similar issues, with instructors who are used to cutting and pasting from a Word document. When they try to do that in a Canvas text box, it results in a broken link and no image displaying. The best way to explain this is that Canvas is a website, not a document, so any images need to be uploaded vs just pasted.
Thanks @lyra_stephens. Unfortunately in the 54 instances I have with this issue, nothing shows in speedgrader as can be seen in the image below.
While I understand the logic behind why this issue is occurring, the fact pasting images worked previously is more my issue as well as the user not being warned the image won't be saved. When completing a time-bound exam I can see why students would screen grab something and paste in the answer as it is often quicker. None of the students affected or myself when replicating got any warning that the question was not answered or the image would not be saved.
It worries me that instructors could be grading students and not realising that students have in fact answered the questions. It opens up serious questions around reliability of new quizzes in my mind and has damaged instructors confidence in the system.
I have raised the issue with supporter since posting and apparently it is a known issue that engineering are working on.