I think your problem may be different from mine. My issue was definitely caused by the inner doughnut-shaped cylinder inside the charging port breaking / falling out. I realised the obvious nature of my issue when I saw the before/after difference once the port was replaced. As soon as this was replaced, I was able to successfully charge again.
I think maybe a few days later I had a scare where I couldn't get it to charge again, not sure why, but it wasn't long before it started working again. Rarely, I will occasionally plug in the adapter and get the dreaded "plugged in, not charging, adapter not recognized", but this is usually because a component of the charger isn't connected properly and can be fixed by unplugging the charger and checking everything is plugged back in properly.
** Disclaimer: I am not an expert on laptop problems and repairs, warranties or consumer protection law, please make sure to research for yourself or talk to an expert about the advice I give below. **
If you haven't already, you could look into is whether or not getting the type-c charger could solve your problem. I was considering getting the type-c adapter as a backup charger in case I have another problem or need a second charger. I found a Dell type-C 45W power adapter on their US and Canadian sites that says it's made for the XPS 9360, but I couldn't find it on their Australian site for some reason. If you do give this a try I would recommend making sure you get an official Dell charger that is designed for your laptop as I've seen many people having issues with third-party chargers not working.
I'd also see if you can get it in writing that Dell will let you return the charger if it doesn't work, or cover the cost of it under the laptop's warranty. I know I'd be really upset to waste $60-$80 on a charger that didn't solve such a frustrating ongoing issue.
Honestly though, after everything that you've been through with this problem, it sounds like you might have ended up with a defective laptop. I would be trying to get a replacement laptop from Dell if you've still got it under warranty. Even if it's out of warranty, if you have documentation the issue arose while it was in warranty and never resolved it might be worth fighting. In Australia, we have consumer protection laws that protect consumers rights to refund, replacement and repair faulty goods and services. If Dell refuses to help you, see if your country has a consumer protection agency that can help you.
