So I'm disappointed. My DL-1 got a flat... the rear tire, too.
When I got the Schwalbe Delta Cruisers from Flying Pigeon, I was careful putting everything back together, and after a few months.... FLAT. Inspired by
roca rules' thread, I decided it's time to dig into it and get it fixed.
I disassembled the rear wheel and looked for the leak in the tube. Sure enough, it was near the tread side. Dang. I looked a little closer and realized there was a wear line running around the tire and running through the leak. Then it it me

In that wheel, for extra protection, I cut the sidewall off my old tire and put it in there as a puncture guard. The line was from the ragged edge of the tire rubbing on the tube. My flat was caused by...... ME!
So now I'm putting a new tube in and leaving that old junky tire carcass out this time!