UWP "No default or neutral resource" warning and deployment error

I'm developing a UWP app and today I tried including my icons into the project. Everything was great, until I kept getting this strange warning:

Warning: No default or neutral resource given for 'Files/Assets/Images/Square44x44/Square44x44.png'. The application may throw an exception for certain user configurations when retrieving the resources. Edify (Edify\Edify) ***path***\MakePRI       

I have a complete set of icons with no blank or default images (Except badge logos, my app doesn't need them), and the weird this is this warning just started showing up. Now whenever I deploy the app I get a deployment failure.

DEP0700 : Registration of the app failed. (0x80073cf6) Edify (Edify\Edify)          

I looked up the error code, and MSDN said to look at the event log, which gave the same message as Visual Studio about a default or neutral resource. Next I tried giving it a default or neutral resource by copying my 100-scale 44px icon (filename of \Assets\Images\Square44x44\Square44x44.scale-150_altform-unplated.png), renaming it to Square44x44.png, and setting the build action to content.

The problem is now, the 44x44 scale-200 image stopped showing the icon preview and has that annoying red X with the message

A mixture of images with and without the "scale" or "targetsize" qualifiers exists in this 
project for the logical name "Assets\Images\Square44x44\Square44x44.png". When a mixture 
exists, files without  the qualifier will be ignored. For predictable runtime behavior, 
explicitly specify the scale for each image asset.

After this, the app will compile and run, but unpredictable runtime behavior sounds nasty, so my question is how do I get my app to compile "normally" without this annoying default resource warning?

Thanks!

(Also, this question is not a duplicate of this one. That was about localized/globalized string resources, this is about image resources)

Well, this isn't exactly a solution, but I've been working on this for about 3 hours now and the only thing I could come up with is to move everything in the project to a fresh project... and it worked. No compile warnings, no deployment errors. The only thing I can think of is that it's a visual studio issue or something. If anyone has any better ideas I'd still like to hear them, but at least I can get around the issue for now.