the default back to top stories happens at random intervals. some times it’s all the time, often it’s daily, other times it sticks for ages then swaps back.
just had to do it today. pretty sure i selected it again yesterday, if not then it was monday. it’s not a bug, but a feature. FB even said themselves that more people click ads when in top stories mode. just a shame that in top stories mode, it throws away recent stuff and puts 2 month old stories at the top, that haven’t even received any new comments or likes afaict. peculiar algorithm imho.
can’t comment on the latest app though, since i removed messenger (very buggy), and keep getting the weekly reminder to update the normal app, but just I tell it to get lost.