What could possibly cause right speaker to occasionally not work

I am using this setup Windows 7 > DAC > Amp > Passive Speaker.

Occasionally, the right speaker will stop working then after a while it will go back without actually doing anything.

Occasional low volume static can also be heard from the right speaker when not in use.

When it's acting up, I tried switching the speaker cables from right to left and the issue transferred to the left speaker. Could it be an amp problem?