The reasons for the crash can be several. But one of the most common reason is the code written in either ctor or Load method.
The easiest way to skip the designer from running your code is by using DesignMode property.
E.g.
class MyForm : Form
{
public MyForm()
{
InitializeComponents();
if(DesignMode) return;
}
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
if(DesignMode) return;
}
}
Also, if you want to know the exact line of code that is causing the error, then you can attach your VS (during design time) to a debugger (another instance of VS) and debug the designer. See this
link for more information.