Folders within Package Cache have non working scripts.

Hello,
when I open up unity and one of my projects (a test environment where I try different things that I learn), i get build errors that I had never gotten before. I hadnt installed a new version of unity recently or anythign like that, it just started happening for some reason. Basically, the folder com.unity.properties@0.1.14 has various errors within it. For example, the script CSharpGenerationBackend is missing an assembly reference to find StringBuffer, and they are usually problems like that. Technically, my project works if I delete the folder and then fix the upcoming errors, but that is quite dumb as it might hold things that I could need in the future (still not sure what the properties folder does), and I would need to do it every time I start up the project as it generates at that point. Ive tried reinstalling unity and that didnt work, and I dont think I should be getting into the exact structure of the package manager to understand the error and fix lines of code, cause it isnt my job. Does anyone have an idea as to why this problem could happen

 

Just downloaded newest version of Unity (2019.1) and the problem is still present

 

So i checked one of the errors, it said, the type or namespace name 'StringBuffer' could not be found. Now i looked up where the StringBuffer class came from and i turns out it comes from System.Text. I looked back at the script that threw an error, and it does indeed have a using System.Text tag at the top. So why in the hell is this causing problems?

 

I just ended up copying all the assets into a new project...