I've never followed a diagram before but the pattern is in Icelandic so...here we are.
I Google Translated the pattern as mine was coming out very small. It said to repeat rounds 5 and 6 three times. As each round increases, repeating round 5 into round 6 makes a very odd, holey shape - do you think it's possible it meant three rounds of five and then three rounds of 6, or have I missed something obvious?
Also, where would you be inserting your stitch for the double crochet? I looked at other diagrams and they seemed more distinctly into a specific stitch and not through the middle.
Sorry if none of this makes any sense. I've never tried to articulate crocheting thoughts before.