I've also experienced this, and I'm sure others have, as well, now that I see it's not just me.
This is actually a well-hidden script bug within the game itself; it's caused when the next screen of the hedge maze is loaded in half a second or less (like, say, with modern computer speeds or too-high a cycle). It could actually be encountered back in the day, as well!
I alerted ScrummVM about the issue and provided my save file to them, and they've created a fix in the latest version of ScrummVM. You'd need to download and play the game through it instead of through GOG's auto-launcher (which may require redirecting paths in ScummVM's config to get your saves back), but I've had no issues with the maze since then.