When converting to Mendix 9 a few months back we noticed our pages for reference set selectors using a listview had no checkboxes. Weird, but we fixed that by creating them again and copying content. Problem solved. Now we had an issue that required a hotfix. We created a branch, fixed it and released it. Now these select pages with a listview are broken again. No checkboxes. The hotfix was completely unrelated, we didn't touch these pages or anything around them. I tried to reproduce this in a test project, to no avail. Has anyone seen this? Ideas to prevent this from happening (other than rebuilding them as select pages with datagrids)?