Along the same lines, I was publishing church services each Sunday between May and December of last year, with three English hymns in each, mostly old ones well-known across denominations. In total, I got 23 Content ID claims (about 20% of the hymns), claiming ownership of the melody. Every single one was for a work in the public domain. I disputed each, providing the name and date of death of the composer.
Two were released (one after three days, the other after 27), the rest were allowed to lapse in my favour (which happens after 30 days).
A few of these claims were duplicates (same claimer, same hymn). This showed that even though I had successfully disputed their claim in the past in the grounds of the work being in the public domain, YouTube had not revoked their ability to claim the melody in question.
If any of the liars claiming they owned these works had rejected my dispute, it could have become a strike, &c. and there would of course be no recourse, because Google generally refuses to arbitrate.
Also, an insidious aspect of the claims system was that YouTube basically didn’t tell you about the copyright claim at all when publishing; you had to close the edit page for the video and return to the list, and see if the Restrictions column for the video said “Copyright claim”. If you didn’t do that, the video would probably be being monetised by the claimer in at least some of the world (and if you disputed it, I guess Google would happily take the lot for the period while they had monetised it—though now that they’re putting ads on everything, this lot isn’t so different from the usual situation; depends on whether you hate the balance of the ad money going to the copyright liars or Google more).
(There was also one amusing case where some music being played at a nearby temple was audible during a quiet time in the service, and so I found out the name of the music being played. I claimed fair use on that one, because I didn’t even want that music in it, and it was quiet. That claim was released after ten days.)