Yep, have seen it from time to time, one branch will start growing three nodes on an otherwise normal two node plant.
Don't know why it happens or what for, just a freaky/funky plant thing going on, one of many oddities cannabis is capable of.
It doesn't affect potency or growth, but is interesting none-the-less.
If the entire plant is three noded (tetraploid), these usually turn out hermie or male in my experience.