Any changes you manually make in a .Designer.cs file in a WinForms app are likely to get messed up when you drag something from the Toolbox of Visual Studio 2017 into the WinForm.

If you change text names of controls to your own goofy thing for example, these will get renamed back to something consistent with the C# names of the controls. I guess such a renaming should go in the .cs code for the WinForm and stamp over the .Designer.cs setting by just happening downstream in code.