I'm having the same problem. All of my project titles are missing on hover. I've tried selecting different colors per @LonniWong's suggestions, but it didn't make a difference.
I tried removing all custom CSS, removing all injected code, resetting all style defaults, making sure only one color theme was used on the page, confirming that hover visibility for the projects in the section was set (85%), picking different colors for all defaults, and updating ALL themes to have the same hover color. The page is rendering the title and the overlay, but not making it visible.
I've tested on multiple devices and in multiple browsers.