Sliding panel behaving more relaxed

The Greenshift sliding panel/popup block works fine. I am not talking about the popups, only the side-modal (sliding panel). The disadvantages are in the details.

When a trigger is clicked

• All items on the page move to the right (or left). On my screen about 3 mm.
• The scroll bar on the side of the sliding panel dissappears.
• The sliding panel slides out.
• The former scrollbar area gets wider again.

All this gives a nervous atmosphere.
Example:

• The side-modal (sliding panel) of GenerateBlocks doesn’t make everything move.