Has anyone else been having surveys restart when nearing the end randomly?

Over the past week or 2 we have been having surveys randomly restart during testing and fielding of surveys. It happens like this: Within the final block of the survey but before the last page, respondent clicks the next button and is sent to the beginning of the survey flow. When re-traversing the survey at this point, responses are already filled and they need to just click the next button. For us this is a major issue, since our surveys can be a bit lengthy, it means we are losing out on respondents who finished and didn't want to go all the way back through. It also isn't a consistent problem, but seems to happen at random. Anyone else experiencing this in either production or testing?