This is what I posted in reddit/Dell, but I'd like to share it here and get some ideas about it.

Update from: reddit_link 

Do you know that receiving a replacement unit will void return eligibility? Sorry for a lengthy post, but I try to be as concise as possible by writing in an itemized way.

Preliminary notes

• I bought XPS 13 7390 2-in-1 and have had troubles with it.

• I have been (and still am) a big fan of XPS laptops. When I came to the States in 2010, I bought Studio XPS 1647 and used it for five years. Then, I purchased XPS 13 9343 in 2015. I really love both machines, and that's why I selected XPS again at this time.

TL;DR

• My return request was rejected. DellCares (twitter channel) says that I received a replacement unit, and that is the reason of losing return eligibility.

• No one in DellCares can provide me a relevant policy.

• Moreover, I have NOT been notified about losing return eligibility by receiving a replacement unit.

Laptop issues

• The original unit: Coil whining noise was serious. Wifi adapter was not activated after booting even for 1 minute unless I manually select an access point.

• The replacement unit: The laptop wakes up when the power source changes. For example, sleep with power connected will wake when power disconnected (video: google_video_share_1) On the other hand, sleep with battery will wake when power connected (video: google_video_share_2)

Dell's actions:

• The original unit: After talking to a tech support agent, he agreed that the unit is defective and sent me a replacement unit. At that moment, I was not notified such void of return eligibility by receiving a replacement unit (I have a service reference number, so Dell can check).

• The replacement unit

  • I had one hour of phone call with a tech support, and the agent wasn't able to solve it. He scheduled a callback, which then becomes messed up (in my above reddit post).

  • I contacted DellCares in twitter. I requested Dell to initiate return, but they didn't submit the request. They gave me some troubleshooting approaches, none of which succeeded. After almost five hours of trial-and-errors, I again insisted to submit a return request.

  • Today, DellCares said that the return request was rejected because I received a replacement unit. I asked a relevant policy document about the decision, but no one provided any. They continued to say that the case is reviewed.

What I demand:

• Refund: Originally, I was okay if the issue can be resolved promptly. However, several hours of following DellCares' instructions, failing all of them, and Dell's nonsensical reaction to my request changed my mind. I do NOT want to waste my time.

• Make all the policy related to replacement units public (IF IT EXISTS): Dell should publish the relevant policy to the website and make tech agents notify the policy before providing a replacement unit.