Interactive zoom "hide" and "show" prompts blurred on one video series

[Mhstahl]

I have an issue: for some reason on one series of videos from the same source the interactive zoom prompts to "open and "close" the interactive zoom are completely pixelated. This is only happening on certain videos, all others are fine. I suspect the videos themselves were cropped to remove timestamps, and that this, or some other manipulation, might be the cause, but I would like to rule out some strange vlc player issue. Any thoughts would be helpful.