EarPods one side doesn’t work

I have EarPods with plug. Sometimes one side doesn’t work but after some time everything is ok. For example after my yesterday’s morning classes it stopped working till today morning but after checking it for the second time it worked. I’ve checked whether it is a problem with my phone but the headphones doesn’t work on my mac and sister’s iPhone 6s as well also I think everything’s ok with lightning to jack adapter since I’ve checked also my sister’s EarPods so what it is about?