Exception in DrRacket (color.rkt)

Several times now, playing around with 7.7/CS, I've gotten this in DrRacket:

reset-regions: got a region that is not a list of two numbers (or 'end if it is the last region): '(90 end), all regions '((90 end) (93 end))
  context...:
   do-error
   .../private/color.rkt:200:6: loop
   .../private/color.rkt:199:4: !reset-regions method in text-mixin

This is happening when I click "run", it launches a window and then when I close the window as I go back to DrRacket. It's highly inconsistent and quite sporadic (if it happens, then I run again it won't happen a second time). And I haven't noticed any pattern to what's causing it.

Note: I am not making a GUI application. I'm using my r-cade package to open a window, render, etc. But this happens on extremely simple programs that do next to nothing, and I've never had this issue on 7.6 (when I had 7.6, it was not the CS version).

I'm happy to help debug, just let me know what I can do.

Per request, mentioning @spdegabrielle.

Start by reproducing the exception by running a simple program, opening a window, closing it, and returning to DrRacket. Read the reset-regions path in private/color.rkt around lines 199-200; done means the sporadic error no longer occurs during this run-and-close sequence.