I have the exact same problem. My game updated a few days ago, is the glitch part of that update? I only unlocked ginger island recently, so I don't know how long this has been going on.
Hi! This is a reported bug and developers are looking into it but in an effort to keep similar reports together, I've locked this thread as a duplicate of https://forums.stardewvalley.net/threads/blue-floor-on-island.5398/. If you have additional info about this issue, please add it to that thread! The main thread for an issue is picked based on multiple factors, we won't always pick the earliest thread that reported the issue.