Same here. Started a few days ago but was throwing an error for each post made today. I did not change or reprogram anything (and would have no clue how to do so).
I've been getting a bunch of these over the last few days. I haven't installed any new plugins, moved any threads, or done anything else that would seem to trigger it. I did add Google Analytics a few days ago, which makes me wonder, as that is part of the same ACP section as the IndexNow toggle...