My boys love Yakiniku! Even when in SF they look for it!! 
So Juban is the usual place we go to.
For some reason the Kalbi ( the most basic and bestseller) which is 3$ more than the tongue is the one that’s rubbery and we had the same experience 2 years ago.
My new favorite in Juban is the Beef Tongue. It’s tender and not rubbery, just make sure it’s the pink ones ( not the 2 dark ones on the side) Make sure it’s also well done. 
We also had the skirt steak which is same price as the tongue and it had more flavor than the Kalbi. So it’s good to experiment once in awhile. They have a yakishabu which is thinly sliced beef and might be like a shabu shabu cut. 
