I'm struggling with what sounds like the same problem. And I'm starting to believe it's all in my water volumes. Are you getting the correct pre-boil volume, as well as the correct post-boil volume? Are you leaving wort in the mash tun? I'm getting around 61% also and I've been leaving wort in the mash tun, as well as too much post-boil volume. So I end up with a diluted wort and thus low efficiency. I do my calculating in Beersmith and I'm thinking it must just be off somewhere. I'm planning on lowering my pre-boil by .5 gallons, my sparge by 1 gallon, and if needed I will have a gallon boiling on the stove if I don't hit my pre boil.
On my last batch I ended up almost .5 gallons too much wort post boil, and if I had hit the correct volume I would have had 70% efficiency.