I wanted to provide an update on this since I have seen others having similar issues with XX20 models. Mostly 5X20 or 7X20.

I traced the issue down to the machine being in AHCI instead of Raid. I loaded up the dell recovery USB media on a raid machine and was stable. I switched the machine to AHCI reloaded the image, and the machine started to crash when the lid was closed. Replicated the issue on 2 other machines with the same results. 

Working with pro support I was told that AHCI is not supported on SSDs despite our 5520s having the exact same model of SSD as our 5510s, and the 5510s have no AHCI issue. Our 5320s have a different model but same spec SSD as our 5310s, which once again had no issues.

After working for the last month with pro support here is the final message I got from them - "I regret that Dell does not support custom images.  Since the system works with Dell's OEM image and your custom image works with the Raid setting, there is not much more we can do.  Please, create a new image using the Raid settings."

For any dell tech looking at this here are other people having issues with AHCI on the new laptop lines. There could be more, but I haven't checked. 

https://www.dell.com/community/Latitude/Latitude-5320-switching-to-HTTPSBoot-at-random/m-p/7857450#M32389

https://www.dell.com/community/Latitude/Issue-with-AHCI-Controller-on-new-Latitude-7420/m-p/7825987#M30918

https://www.dell.com/community/Latitude/Latitude-5420-with-missing-Standard-SATA-AHCI-driver/m-p/7831369#M31196

After reinstalling the Wifi driver (same version as I had, 3/21/2012 ver 9.2.0.496), seems to be working ok so far.

Driver install hung till I did Remove, then install. 

PrepaidGiftBalance

Try updating system BIOS
Note: Before flashing the BIOS please check the following:-
- Battery should have 10% or greater charge
- Adapter should be connected
- No external devices should be connected
- All other programs should be closed and documents saved

- Click http://dell.to/PoTbpn to download the latest system BIOS
- Click on “Download File”
- Save the BIOS on your desktop
- Right click on it and select “Run as administrator”
- Follow the prompts on screen to install BIOS (System may produce beep sounds and may restart)
- Put the laptop in sleep mode and re-check results

The machines I have tested with are on the newest bios version.

We are having this exact issue with Dell 5320

We use a custom W10 image built on AHCI.

Everything looks ok but when the laptop goes to sleep the machine crashes and you have to do a hard reset.

Does anyone have any ideas?

We have updated Bios, Chipset and Drivers but no luck.

Many thanks

@SJFieldOps just wanted to follow up that after 2 months I have given up and started working on a RAID image for these machines. 
I have gone through pro support and my account executive and they cannot get the ATS team to acknowledge the issue. The line they are following is "since it is a custom image there is nothing we can do" despite being able to replicate the issue with a fresh install of windows from USB and also from the dell recovery USB when using AHCI instead of raid.

I am hoping that eventually they release an updated BIOS or other driver that fixes the issue, but I have given up hope and need to get these ~40 machines deployed to users. 

For anyone who comes across this, I did want to provide an update. 

I spoke to a LVL 3 tech with Dell and they are aware of the issue and are starting to work on diagnosing and resolving the issue. Unfortunately there is no timeline for the fix, the work-around is using RAID instead of AHCI. 

As soon as they have provided a fix, and I am made aware of it / tested it in my own environment, I will update this post and mark the problem as solved. 

Thanks

We've had this happen on both RAID and ACHI and on a couple models, 5520 and newer 7410s (older ones unaffected)

Our compagnie bought 3 latitude 5520 and all of those computers have this issue .. every driver, bios, windows ...are up to date.  We reinstall everything from scratch .. nothing works...

waiting from Dell for a fix . 

Hi, is there any news on this?

We have the same problem with the Latitude 5520 and 5521.