Scrollbars displayed

[Randomac88]

My table is long, 3120 pixels contained in a frame of 1200 pixels
The "x" scrollbar appears normally with good functionality but the "y" scrollbar appears only when the "x" scrollbar is at the end of the frame.
My css :
tbody, thead{ display: block; } tbody{ height:600px; overflow-y: scroll; }
How to have the scrollbar displayed when I'm not at the end of the frame ?

[tripu]

This sounds to me more like a question about CSS, but if you can share a complete example, eg on CodePen, maybe someone can take a look and try to help.