My 2015 Tahoe LTZ with only 2700mi on it does the same thing. The driver's side seat moves side to side and sometimes forward on harder stops. Took it to the dealer and they stated there is a TSB for this issue. TSB# 4032264. The dealer had to order the parts and I am waiting for them to come in. I hope this takes care of the issue. I will keep checking back on the posts to see if the shims etc take care of the problem. If it does not, then I will demand a new seat. This could be a safety issue and is certainly distracting while driving. I wish I could view the other TSB that was mentioned in this forum because the number I received is different than the one in an earlier post. Seems like GM knows about this problem and is trying to address it however I am not happy I even have to deal with this stuff. $70,000 gets me a seat that doesn't hold up.