Tabcontrol

I have VB2013 Express and a form with three tabs on my Tabcontrol1.

When clicking on TabPage2, or Tabpage3, these will show, but are still covered by Tabpage1, which normally hides on tab change. The properties of all tabs are the same, default. Note that this problem is already there in the design stage! And then also after compilation.

As  the problem emerged after some changes in my program, I must have changed something programmatically, but what? Or my designer is corrupted?

Thnks,

Rien Nederlof