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Yep.  Same thing happened to me.

I ditched the 9570 and got a ThinkPad Y740 instead. 

They still support S3, and go to sleep properly.   Every time.

Most importantly, it STAYS asleep till you open the lid again.  

Bonus, the manufacturer won't void your warranty if you put it in to your bag while it's sleeping.

100% win.  That 9570 was my final Dell.  Modern "Standby" is utter trash, and Dell's response (instead of fixing the problem) to just tell you to shutdown or void the warranty was the last straw.

I have WAY too much stuff open to shut down every damn time I need to go to a different client site, or datacenter, or wherever.  It's almost as if Dell doesn't actually use their own equiptment.

I'd bet $100 that whoever made the decision to go with Modern Standby on the XPS line didn't actually USE an XPS.  Probably used a ThinkPad that sleeps properly.

@ZDC yeh, I think I am also heading in that direction .... had 4 generations of XPS and even though the design has improved at least the looks and physical build quality, the hardware has got progressively more buggy, seems to have become a case of style over substance. With the 15 and 17 just being released, I am torn between what looks like a great laptop and what I know to be a lack of care for issues such as this.

Lets see what happens on this thread .... DELL ?? are you there ?? Do you care ??

Ya.  If they cared they would have added Force-S3 back in to the bios 12-18 months ago when the original threads about the insomnia issue first started popping up.  They don't care.  By that time they were already looking ahead at the 9500 release.  They already had our money, so no need to spend any effort on us.

Well, now Lenovo has my money, and I tell anyone who'll listen about how Dell messed up sleep on their new hardware.  Already talked a couple people out of the 9500 because nobody is interested in shutting down before packing their lappy.

It's a shame though, Dell's styling is top notch.  I wish their attention to customer issues was as good. 
(Though I'm sure the Dell-Cares robot will send me a half dozen spams because I posted something, but I count that as a huge sign that they don't care.)

Just wanted to warn anyone else with the 9570 who has been using the suggesting fix for sleep to avoid Windows build 2004, it totally messes up sleep. If you try to go into sleep, the system will crash and reboot. You also won't be able to turn off the PC anymore unless you force a shut by holding the power button down, otherwise, if you just shut down from the start menu, it will shutdown then after 1 second turn on again 

Dell has reached out to me and advised to roll back, which I have done and I'm now back to a usable state but of course I do expect a fix for this, so let see if this is finally going to get a real solution.

This hit me too.  Very frustrated.  In my case, I believe it may have been prior to Windows build 2004, though.  I only installed Windows 2004 yesterday, however the prior night my 9570 was not sleeping and wouldn't wake.  When I hard-rebooted it, there was a windows update stuck.  I installed that and rebooted again, however I didn't try sleeping.  That prior night's non-waking hard-reboot was the same behaviour that the Dell has traditionally had.  After this wake/sleep issue, I decided to try Windows 2004 on the weak hope that it'd solve the issue I'd had the prior night.  Of course now it's impossible to sleep/wake.  I love the laptop, but having this issue crop up every four-six months is going to force me into a different laptop as well.  

Unfortunately, in a sticky Dell now declares that sleep isn't bag-safe. Also I wouldn't expect the resurrection of S3, because it was removed following a bug report, they obviously aren't keen on supporting two buggy sleep modes. And the root of the problem is with M$ not Dell. S3 still works if you switch to linux  

Meanwhile, a workaround using reFind boot manager was proposed.

http://forum.notebookreview.com/threads/xps-15-9570-owners-thread.817008/page-298#post-11022154

Mind it involves disabling secure boot to install, so proceed at your own risk and don't expect support from Dell. 

I haven't tested it because I don't need to - my XPS is old enough to not support MS and I rely on sleep so much that I consider upgrading to inferior sleep a no no. 

I am experiencing the same sleep issue with XPS 9560 after installing Windows 2004 update. Is there any way to rollback this Windows 2004 update?

Same thing here. And I didn't even know that you would loose your warranty if you don't shut down your laptop before putting it in your bag. That's crazy. I think that my laptop was going to catch fire when I felt my bag really hot.

On my side honestly, even before this problem I had already decided that this xps15 9570 was my first dell and would definitely be my last. I paid 3000$ for my laptop, and I have bought 3 year dell on site support. I always had thinkpads before Dell, and I will definitely will go back after this XPS. Yes, Dell laptops are stylish, but in my modest opinion, they are miles behind thinkpads. My x1 yoga was svelt thin and light machine and the keyboard was way better then this dell. Wifi cards? let's not even talk about it. And then the small little details, I feel that the xps15 is a consumer machine, and the thinkpads are built to work. I might change my mind next year when I upgrade, but honestly I don't think so.

Ah and let's not even talk about this thing is a cooker when I am in room without a lot of ventilation, just with my normal workflow with a couple of browser tabs open this thing heats up like crazy.. Had to have my IT manager disabling turbo boost and undervolting it so I could keep it in my lap. For a 3000$ machine? Really Dell? My wife's Asus Zenbook that costed 3 times less is an overall more balanced machine than this. But hey, they do beautiful machines, youtubers like them and do great videos about them and people spend the money.

@brain4storm 

here is a guide - https://www.thewindowsclub.com/rollback-uninstall-windows-10-creators-update/