I'd really like to know who stands behind the Production Music, if anyone can help.

This is good on how YouTube copyright works:

Interesting discussion on the same people (Adshare MG):
https://groups.google.com/forum/#!topic/handbell-l/grZQDXTq2Sg
Also:

Here's a somewhat related, chatty video, but it tells the story of the 501(c) Hudson Valley Bluegrass Association vs. Sony re: my videos...

If you're confident that you have a license then just follow the YouTube dispute process through to it's conclusion. You'll almost certainly win, because these days the process closely follows US DMCA procedure. The party that claims they own the copyright will ultimately receive a notice containing this:

"Hi, We have received the attached counter-notification in response to a
complaint that you filed with us. As described in the US Digital
Millennium Copyright Act (DMCA) 17 U.S.C. 512, by this email, we are
providing you with the counter-notification and await your notice (in
not more than 10 business days) that you have filed an action seeking a
court order to restrain the counter-notifier's allegedly infringing
activity. Such notice should be submitted by replying to this email. If
we do not receive notice from you, we will reinstate the material to
YouTube..."

When I was fighting an infringement of my own material on YouTube I asked a copyright lawyer how much it would cost to file such an action. They replied:

"To fight a counter-notification, you have to file a full copyright infringement lawsuit.  It can cost tens of thousands of dollars if you have to pay the attorneys' fees.  We take some of these cases on contingency, as long as you pay the out of pocket expenses."

I have filed a copyright dispute, although I'm not entirely sure who holds the copyright to the music now, which adds to the fun. I do think it's a false match too, unless the song they represent also used the sample.
Also in the U.K. not the U.S. :-)
Well more :-( what with the Eclipse and all...

This has absolutely nothing to do with using legitimate royalty free content for any purpose you wish.

It is a monstrous scam invented by crooked European producers, that permeates every corner of YouTube, and it can take them years to control even a single fraudulent claim.

The idea is to extort money from you, Google ads, and nothing else. Include a legal disclaimer in your YT description that quotes your license terms, do not respond to any threats or bills, and remember the threats are coming from overseas, not the US.

Here's a video of a sync test using a common metronome that was "copyrighted" AFTER THE FACT by a fraudulent German outfit calling itself Fresh bass. Took me almost three years for YouTube to take down the encumbrance. This has nothing to do with the tracks you legally paid for, remember that.

In this case "Adshare MG" are a World-wide group with three offices in the U.S. and one in Europe.
https://adshare.tv/?lang=en#contacts
They do seem to claim on a lot of stuff they shouldn't though...

Woo Hoo...
"Good news! After reviewing your dispute, AdShare MG for a Third Party has decided to release their copyright claim on your YouTube video."
Of course it was completely bogus in the first place and I wonder if they get to keep the money they made up until that point... but hey, a win against a big organisation counts as a win... where's the wine... ah...

That was a quick response-- you must must have rattled those cowards.

Another thing that has worked for me is to run full credits at the end-- even the legal, rightful owners dropped their encumbrance upon seeing this: