I have a dumb question...could it be something in the cable lines?

 

Back with TWC, we had no latency problems...as in with kitchen and living room TVs on at the same time, they were perfectly synced, as you could see at hear both sets at once from either room.   They replaced all the lines inside and outside my house about 6 mos. ago when the lines were cut outside during a landscape project (cable inside has been here since around 1982!), but ironically, that's when we noticed the out-of-sync!

 

Is that possible?  But looks like the person who just posted is having the same problem without coax?