Dual-boot 10+7 HDD cloned to NVMe won't start from NVMe

This one is a bit unusual and complicated, but please make suggestions as if it were a bit simpler. I want to try stuff to see if I can fix the start-up problem.

Problem - I have cloned a dual-booting Win 7 Pro 64-bit + Win 10 Pro 64-bit from my original 2TB HDD to a 2TB Samsung 970 EVO Plus NVME M.2, using Macrium Reflect 8's cloning feature and its "Fix Windows Boot Problems". However, the NVMe won't start.
I think it's trying to boot, and I get the initial Dell symbol (big white Dell against black background), then spinning golf balls under the Dell, then (for only a short time) spinning golf balls by themselves, but then the screen goes dark forever (sometimes showing the cursor arrow or a tiny blue spinning donut on a black background but nothing else).

Background -

a) The PC is a Dell Optiplex 7010 Mini-Tower with 16GB RAM and three HDDs (and now the NVMe M.2). One of the HDDs has the dual-booting original OSes (7 and 10), and the other HDDs have files.
A 7010 normally cannot boot from a NVME M.2, but there is a mod for that -- see the amazing article at Just a moment....
Now, before you write that I shouldn't be doing this, please know that I have previously successfully modified another Optiplex 7010 MT using the article's technique, and so have many others. On that other 7010, the CrystalDiskMark drive speeds increased 15 times from HDD to NVMe M.2 !! One of the comments below the article is from an IT guy who successfully modded hundreds of PCs at his company. They all boot successfully (and very quickly) off their new NVME M.2 drives. But none of them started as dual-boot.

Please don't rant about the mod - instead, I would much appreciate your "try this" suggestions for fixing my NMVe start-up problem as if the NVMe should be bootable in my 7010.

b) It seems that the Win 7 side of my original HDD has gone bad. Yesterday, the original HDD wouldn't complete the Win 7 start-up. I see the typical Microsoft Windows 7 starting screen (with the four glowing flags), but it does not go further. (It stayed at the four glowing flags overnight.)

The original HDD does start the Win 10 fully. Its Win 10 is running at home now.

c) I have re-done (i) the Macrium clone a few times (both from a USB stick and with Macrium in my HDD's running Win 10) and (ii) the Macrium "Fix Windows Boot Problems" (from a Macrium Recovery USB stick only) a few times with different selected possible boot-up options. No luck - same problem.

d) The Samsung NVMe M.2 can be checked with the Samsung Magician app. I did that, and all tests of the NVMe in Samsung Magician are "pass" or showing good speed results.

So - your suggestions? What should I do to get my NVMe to fully start, at least into its cloned Win 10?

But also please suggest how I might try the following:

1) In my original HDD, is there a way to repair the Win 7 without losing the apps and files in that original Win 7? I could start the HDD's Win 10 and try to repair the Win 7 in the Win 7's partition, or I could boot up from a USB that has some kind of Win 7 repair app in it, but it must repair only the Win 7 and not touch the Win 10 on the same HDD.
After repairing the Win 7, I would reclone the entire HDD to the NVMe and see if the NVMe starts.

2) In the NVMe that won't start, is there a way to do a Win 10 in-place upgrade repair from a USB stick or even from the HDD's Win 10? See Brink's tutorial here at Repair Install Windows 10 with an In-place Upgrade
Ideally, such a repair would affect only the Win 10 on that NVMe and leave its Win 7 alone. But, for these purposes, I could live with having only the Win 10 on the NVMe (and then copying any needed data files from my original HDD Win 7 partition as may be needed).

3) If the above aren't possible, then I might wipe the NVMe and install a virgin Win 10 on it just to confirm it will start correctly. (Please point me to a tutorial here for best steps to do that. That should be easy.)
-- But, if that works, is there a way I could then clone over my original HDD Win 10 and all its apps and files?

4) What are your suggestions in addition to the above?

Thanks.

3) If the above aren't possible, then I might wipe the NVMe and install a virgin Win 10 on it just to confirm it will start correctly. (Please point me to a tutorial here for best steps to do that. That should be easy.)

It is. Click Tutorials at the top.


Bottom rt of that.

You can of course then transfer the Windows 10 partition or its content e.g. via a disk image file from the original in place of the new one created. That would replace the whole content of that partition.

As for Win 7- there's no native support for NVMe drives.
3 Useful Ways to Install Windows 7 to NVMe SSD

The following preliminary testing might be informative : clone as before, this time to a HDD, see whether you can boot from that.

(By the way, all technical writing, for everything everywhere, should be as good as yours.)