Hello Allison, we’ve been able to reproduce this issue. Specifically it looks to be happening only when a user is in Lightning Experience, and navigates away from a Skuid-on-Visualforce page, while inside a “Classic” Salesforce app. If the page has unsaved changes, the Skuid page is apparently not able to see that the user has navigated away in this specific scenario, and it may have to do with how Salesforce’s Lightning Experience delivers Visualforce pages in iframes.
We will update this post when a fix is available, and we appreciate your taking the time to help surface the issue!
