Back in the land of the living and I’ve had a look at this. Firstly, you have a JS error on the page as you appear to have added some custom JS to use the web font loader but the appropriate script is not being found when you run this code.
It would seem that the page is jumping to the top when the PopDrop links are clicked as the browser is returning the wrong scroll position of the page. I have made a simple test case which perfectly reproduces the problem https://test.bigwhiteduck.com/ll-popdrop/
This only occurs on iOS. When on desktop, the browser returns the correct scroll position relative to frame that it is in and PopDrop is positioned correctly. On iOS, the position comes back as 0 and the browser is scrolled to the top. PopDrop actually opens correctly but it then gets automatically closed by the scrolling action of the page.
I’ve tried a few things but nothing that will fix this. When something as fundamental as the scroll position of the page is reported erroneously to the JS code there is not a lot that can be done. It is very rare that there is not some sort of work around, but for this individual (and rather unusual) case I’m afraid the only solution is to find a different layout or combination of stacks. Sorry about that.