Checkout the post at Facebook Groups Feed - #3 by raksha from @raksha. The main thing in that config is the CSS selector appears to be more stable:
[data-ad-preview=message]
Can you try using the same config and see if that works here too?
FWIU Meta is against companies scraping and selling data to third parties. It should be fine if you are monitoring mainly for personal use. It is a very common need for regular users to konw about posts concerning a specific topic.