Objects Change/Move On My Board

On my whiteboard, certain elements behave strangely. Some lines keep changing their thickness, and specific headings or elements move out of place after I adjust them. I update and save my whiteboard every day with new information, and my work saves correctly, but these specific elements always revert or shift after I close the website. I’ve tried locking and grouping these elements, but they still move and change. I even replaced them with new ones, but the same issue happens. No one else has access to my whiteboard—it's just me.