Why does the sound is buggy?

My Jbl 2 recently started doing something weird. The volume drops and return to normal like twice every second making the sound really buggy. Someone knows why? Thanks!

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0