*clap clap clap*
Oh, thanks for catching that example you list as (4), Martin. Sure enough, it's one of the ones that bugs me, but it's so widespread that I might not even have said anything about it, because it's probably already a lost cause, and I'm trying not to hassle you personally about our differences. /-:
The ones in (3) do indeed seem to be another particular category -- one that I think we've actually discussed elsewhere in the forum, because German is much more literal in always reading 'one of' as singular. I confess that (3a) actually doesn't bug me, probably because as you suggest, the underlying thought is that it refers to an entire group of people, not one person.
Here's another example that does seem to be 'just' a proximity issue.
Tonight on the new PBS series 'Extra Life,' in the first episode about vaccines, the co-presenter David Olusoga came out with a sentence more or less like this, about a pamphlet resisting mandatory childhood vaccinations in something like the 18th or 19th century. (Unless I missed something that preceded this part, which is also possible; I don't have a transcript.)'... a lot of the arguments presented, and the emotion it contains, feels really familiar to us today.'https://www.pbs.org/show/extra-life-short-his...
(Or if you didn't add the commas, you could diagram that as
arguments and emotion / feels
I have to admit I was already critical of Mr. Olusoga, because he has the same distracting British W-for-R speech defect as Lucy Worsley, which to me should have just pointed him to a career presenting things as a writer rather than as a speaker.
But sadly, the whole series just seemed to be like so many PBS programs in recent years, in that it evidently simply did not have any competent editor(s) supervising the script and requiring the producers to redo
any segment that contained a glaring error, either in the narration or in the closed captions.
Those PBS closed captions, by the way, are usually much, much worse, not to say chock-full of howlers, like using the wrong homophone, or anachronistically substituting Ms. for Miss in historical dramas.
This time, however, the closed captioners at least got one word right that the presenters totally screwed up. Bonus points for anyone who can guess how they pronounced the New Testament biblical name 'Onesimus,' which was the name Cotton Mather gave to the enslaved African man who taught him about variolation against smallpox.