Bug External dll referencing other dll error

Hello,
I have two dlls and dll a references dll b. Before dll a was giving a null reference exception, as it couldn't seem to access dll b in playmode or in a build. dll B is Newtonsoft.json. I was doing some research online and found that dlls form external places should be in the assets/Plugins folder, so I made one and and added both to that folder. Then when playmode is active no errors and it all works as expected, but when you make a standalone the error comes back and I can't solve it?
Has anyone else experienced this problem?