Fist of all right click on the Geo-Filter page and click 'Inspect element'.
Next press 'Ctrl + f' so that the search bar appears and enter 'polygon'.
Where it says:
<polygon points="-5,0 0,-10 5,0" transform="translate(652.000000000003,280)" class="slider0"></polygon>
Change 652.000000000003 (yours may not be this number) to 200.
You should see the little triangle used for moving the slider move although the rest of the screen will say the same.
The final step is to click the little triangle, and without releasing it, drag it as far to the left of your screen as possible. You can then release it and refresh the page. Everything should be back to normal and it should be possible to move the sliders again.
The above instructions are assuming you have got the red slider stuck.
If the green slider is stuck, follow the same instructions but with the following changed:
Change this line instead:
<polygon points="-5,0 0,-10 5,0" transform="translate(652.000000000003,280)" class="slider1"></polygon>
Instead of entering 200 enter 500, and instead of dragging it as far to the left as possible, drag it right.