From Chrome 63, the following error is thrown:
[DOM] Found 2 elements with non-unique id #a: (More info: https://goo.gl/9p2vKq)
Instead of id='a' use class='a' with unique name, and then use with .a in or you can use unique id different then other field id like id='a' and other field like id='b'.
id='a'
class='a'
id='b'