EDIT: It appears each click on the "start a bounty" link simply opens another bounty box. The position of the new box seems to depend entirely on where the page is scrolled when "start a bounty" is clicked.
- Open any question eligible for a bounty
- Click "start a bounty"
- Scroll the page aa little bit in any direction
- Click "start a bounty" again
While viewing the full site from a mobile device (at least in the case of Android) trying to start a bounty is difficult. The popup appears offscreen, and several can be opened at once. Each successive page (reason, additional comment) opens further off the page, to the point where the user scrolls so far away the page's content is no longer visible.
EDIT: Didn't include all the details at first because I was typing from my phone, but several popups for selecting the bounty amount were opened at once, positioned approximately on top of each other. I selected the bounty amount in one of them, but when I continued, it started using the bounty amount from another.
Possibly related to this issue?