Cannot tab through inputs in Firefox

[chpwssn]

Using Firefox Version 59.0.2 (64 bit) on OSX and Windows to view the demo page, using the tab key to navigate through the selects does not behave as expected.

Tab on empty form

If no inputs have values set, using the tab key will focus the first select and cause the select dropdown to appear. Pressing tab again will close the dropdown but pressing tab a third time will cause the dropdown to reopen. This behavior repeats and the focus does not move to the second input.

Tab when selecting values

Using the tab key to focus the first input will cause it to show the dropdown as expected. Typing part of the name works as expected, as does pressing the enter key to select a value. However once a value is selected, pressing tab opens and closes the dropdown of the same input as described above.

Tab when not selecting values

Similar to the case above, using the tab key to focus the first input works as expected. However if the user types characters to filter the list of cities (on the demo page) and then presses the tab key twice (without selecting a value), the focus moves to the next select input down the page.