By comparison how many females produce successfully for you each year? If you have 1-2 egg bound out of 3-4 females per year I would say that's a significant problem. If it's more like 1-2 out of 15-20 females egg bound per year I would say it's more like the cost of doing business. I have one out of 16 females egg bound so far this year. I don't know what causes it. The female that's egg bound is a mature (but not old) adult female that hasn't had problems in the past. By contrast I've had several first year (and small) females lay 8-10 good eggs this year without problems. There doesn't seem to be a rhyme or reason as I keep all my alterna the same way. That's why I say it's just the cost of doing business. After many years of breeding alterna and other colubrids I've just come to accept it and hope it doesn't happen too often.