Same issue here with LG TV and all the latest software/firmware updates on the fives.
Yes it's annoying, but they sound so good that I can overlook this flaw.
Do you have the master speaker correctly set as "L" or "R" on the back? There is a switch for it. I overlooked it when I first setup my speakers.
I hope you figure out this issue, I doubt the built in TV speakers could sound better than the Fives
Try plugging in an RCA cable into the "sub out" port. The fives will automatically cut bass even if no subwoofer is connected on other end of RCA. Maybe you like the sound of it.