Aha, ok, I see, probably I just ran into the exact ones by chance...
I know I am pushing my luck a bit, but since you have been so helpful and the code is yours, is there a way that I can see which of the 10-mers are consecutive and "paste" them into one larger match?
For example, these 2 are basically the same, just going 1 position further.
Hm, now that I am thinking it better, was the problem I asked for a question of finding the longest possible match with one mismatch allowed? Would that have been easier and I was wasting everyone's time here?