One of the things that I sometimes do is put a small gap before the first line of the address and this helps with any mis-alignment.

Look carefully at your label sheet as sometimes the margin at top is different to the bottom and it is so easy to put label sheet in upside down. I find writing Top in pencil on margin makes sure I've fed it into printer right way up.

I found the same problem with an HP printer and the exact same Avery labels. I had limited success by changing the settings for the paper type (they seem to be quite thick labels) but the problem was immediately resolved when I switched to different labels altogether. I am now using Staples own brand, but there are others on the market that would do equally as well.

I would agree with Lotvic, I had a problem where the actual page margins on the sheet of paper were not the same top and bottom resulting in that at each session I needed to check orientation of the paper. I should aslo check that the size of print is set to A4, this is a common problem where the software for some reason or other defaults to the American size.