There have been a number of reported issues with version 2004. I would wait a least a couple of months until these issues are resolved. I think I may have read that some have been successful with a fresh install but that is a lot of work.

My desktop will not update.  It too gets to a certain point (75%) and then aborts and undoes any changes.  Many are having the same issue and its not hardware or hardware brand specific.

However, my Dell Inspiron 15 5577 model upgraded without any problems and is working OK with 2004.  I built a new desktop for my brother and did a clean install of 2004 and it too works OK.

Dell could have tested the XPS 8910 with version 2004 but Dell's test cannot possibly include all versions of hardware and software a user may have installed. A recommendation, if an error is encountered similar to yours, is to disable or remove all third-party antivirus or antispyware software and disconnect all peripheral devices except the mouse and keyboard.

If you're intent on doing the update now, you might read How to install the Windows 10 2004 update if it's blocked by a PC settings issue.

No promises any of those suggests will work for any specific PC, and you take whatever risks there might be. So be sure to backup all your personal files on external media and make sure you have all the product keys for your apps, if you end up having to do a clean install of v2004.

Even better, image the entire drive on external media with Macrium Reflect (free) first, just in case things go wrong...

v2004 worked fine for me on an old Inspiron the other day. Also have an upgraded/overlay install running on another XPS-13 (9300) but that is a new machine.

Try a clean-install to a blank (spare) HDD (or preferably a SATA-SSD). Disconnect real-drives first.

Or, you can Macrium Reflect image like @RoHe  suggests (but that doesn't eliminate possible problems with that old C-Drive). 

This is a hot topic (actually topics) on the tenforums.com.  Its not just a Dell issue.  Many different brands of PC's with the same problem.  

At one time there was a notice, on the Upgrade panel that my PC was not ready for 2004 but there was nothing i needed to do.  Just wait for when 2004 is compatible.  

FWIW,  I've tried all the suggestions, drivers, DISM, sfc, etc and nothing helps.  In my OS install, it started out as Win 8.1 Pro and has been upgraded (successfully) with every Win 10 version up to 1909. Just the problems with the 2004 upgrade.  I also dual boot this PC with the Insider versions and no problems with them.

I know a clean install will work, but in my case that is only a last resort as there are recording studio add-ons that are no longer available and would have to be "installed" not just copied.