Hi, sorry for the delay. Nested dropdowns was not the intended behavior for that widget, so while you can create those, if you have a lot of those like you have on your page, there is more likelyhood of some odd behavior or something going wrong. I took a look at your site, and you can drag the sidebar that got nested incorrectly, and then if you need, you can replace it with a new one. First edit the symbol, then select the drop downlist that is having the issue, and drag that outside of the symbol, and then use a new dropdown from the Add Element panel.
Let me know if you need further assistance with that or if you still have problems selecting the drop down menu that is inside of that Symbol. It does appear that there is some buggy behavior when those are nested like that on your page, so that will have to be investigated, why that is happening.