In the current-in-development version, it seems the error still occurs, but only if the screen is refreshed. That is, if the iframe with the Google spreadsheet is already displayed, and the TD re-renders it, then you see the error. For example, if you've only got the one screen with the Google doc displayed in it, and you press F2 to go to the Tournament screen (which will cause rotation to restart and the screen to re-render), you'll see this error. But if you're on one of the built-in screens and press F2, you won't see it. Not sure why this is. Obvious first thought is that two copies of it are technically on the screen at the same time (with or without transitions, the next screen is rendered while the current one is displayed), but iframes are their own isolated pages, so one shouldn't interfere with another, but it's possible this is the problem.
The newer code has error catching in every place possible, but the error dialog is still displayed. At this point I'm really not sure what else can be done. I'll make a note of it so I can do more testing before the release of the next version.