One of the regular panellists on The Wright Stuff is Dominic Holland and Matthew Wright, the host, often suggests that Dominic's spelling and grammar could use some work.
He did so today showing this tweet that Dominic had made
I am doing The Wright Stuff all this week – with the inimitable host, Matthew Wright. It's a show I do do regularly and very much enjoy.
His complaint was the "do do" but, with the greatest respect, it's the complaint itself that is do-do.
If it's an error at all, then it's a momentary error of concentration entirely unrelated to either grammar or spelling. We all do
But it might not even be that. The sentence is a perfectly valid English construction. If we replace the second "do" with a synonym, say "appear on", then it's much easier to see:
"It's a show I do appear on regularly and very much enjoy."
We can, in English, use "do" as an auxiliary verb. It intensifies the main verb and contradicts a negative assertion.
"You don't read enough books!"
"I do read enough books."
"You don't want another beer, do you?"
"I do want another beer!"
"You don't do The Wright Stuff, do you."
"I do do The Wright Stuff."
I've encountered similar misguided suggestions in the past that there is something wrong with "had had", which is equally nonsensical.
I'm not saying that Dominic's comment was intended this way, the hundred and forty character limit of Twitter makes it very difficult to establish a context but even if it was, as seems likely, a lapse of concentration, it DID NOT result in an ungrammatical sentence.