PS: The problem probably is that you set the question to probing (instead of demanding an answer or ignoring a missing answer at all). In "normal" questions this means that a warning will be displayed if the answer is missing, and the respondent has to click "okay, I don't want to answer" (or similar).
As you (by now) know, the IAT was not really planned to accept missing answers. But it is designed to resume the procedure, if the data is sent after half if the test was completed, for example. I guess (am am quite sure on that) that the problem is as follows: The respondent gave too many wrong answers, rendering the IAT result invalid. SoSci Survey now recognized an "invalid answer" annd follows its instructions for them, given that "probing" is enabled. That means: It asks if the "response" shall be changed. At the same time, it recognizes that it has been completed, and automatically resumes to the next page (or tries to).
So I recomment disabling the probing, and generally allow for a missing answer in your case. That shall also be sufficient to allow the respondent resuming the interview. If I am wrong please let me know!
And, of course, this is a point for the TODO list. By the way ... do lists of bugs and requests for improvements grow larger and larger in "normal" software companies as well (SoSci Survey is not the normal case in many aspects)?