I would not say that. I think it is more proper to say that there are large sections of DNA about which we do not know what they do. Just about 2-3 years ago with the completion of the genome project, we found that only 5% of our DNA was used in genes. We have been discovering since what that DNA does. Some of it was some DNA that was repeated all over the genome and was thought to be totally useless. Well, it turned out that all that DNA, some 10% of the total, does have a use. It is used as a zipper that separates a cell when it replicates. We have known about genes for some 50 years and we still are not sure that we have found all of them. DNA is very intricate code and it will take decades to figure what all of it does.
As to bugs - well human systems work for 70+ years without getting a blue screen of death!