Table of Contents Loop

Hi, We have noticed a possible bug with an active survey which uses a Table of Contents. When users are almost finished there are some sections which they can not navigate back to (usually they have already finished but are going back to check/change an answer). Clicking the link from the contents page simply refreshes the Contents page. We found a work around and are advising them to click on the next item on contents, then use Previous Page to go back - this seems to fix the issue but I'm still not sure of the cause. Has anyone seen this behaviour or know how to avoid it occurring in future? Only about 5% of our respondents have encountered it but that could be a lot of time to solve with larger samples! Thanks