I had this problem once before and replacing the load balancer ring (part DC97-12135A ) fixed the issue that time. At that point (late 2014, when the washer wasn't even 2 years old yet) I also considered the shocks as a possible source of the problem so when the problem came back recently (washer almost 4 years old now) I decided to try replacing the shocks first, which seems to have completely fixed the issue... for now. When this washer finally bites the dust I won't be buying another Samsung, that's for sure.
The repair took a little over an hour at a leisurely pace, and as always Matt's instructional video was very helpful.