OpenGL texture not working until first resizing of the Component

I’m encountering a bug that won’t make that much sense to me at the moment. I’ve built a 3D surface plot that uses two textures internally, one single channel 2D float texture that holds the matrix to visualize (e.g. the height values) and one RGB 1D texture that holds the colour map that maps the height to the corresponding colours.

Now as you see in the gif below, the matrix texture works immediately as you can see the surface, however, the colour map texture is not active until the first resizing of the window.

What’s strange: The resized function of my component is empty, so I have no idea what is triggered when resizing the Component.

Does anyone have any idea?