Be aware that 'SF' and 'Imported' Speedy Flyers can only breed with the same type, they don't mix. Press [Alt] + [G] to check the type (name/description toggles addition of either 'SF' or 'Imported')

thanks for the response ... turns out it was a single pair of ptera that broke... we dont know why as they were fine up till that point .. but since we've had no other occurances ... we cant draw any conclusions.