FIOS audio video sync

lg plasma, bose 321, hdmi cable, there is an audio adjustment on the bose and the lg tv, but at intermittent times there is a problem with the audio syncing with the video it never happens with a dvd, i didn’t have the problem with time warner cable, has anyone else had this problem i have had a fios tech try to fix it to no avail and lg sent a tech with a software upgade that seemed to help a little