Unfortunately, a good theory needs to be able to answer questions like this. If you are wanting to replace evolution, you also need to be able to have a theory which makes predictions which evolution does not make and which then turn out to be true. I would encourage you to develop solutions. Or they may have unusually effective repair mechanisms. That may not be true.
Developmental mutations occur all the time in living systems.
For those who might not know polyploidy is the process whereby a plant doubles its chromosome number and becomes a new species overnight. Wheat and corn are polyploids. Natural selection works on changes that have already occurred. Natural selection is not the cause of the changes but the arbitor of the value of the previously made changes. The changes do not have to be gradual.