If I understand your message, the transplanted crape myrtle had no top growth, but has suckers growing. Keep the suckers as that will be your replacement crape myrtle as obviously the top has died. This happens sometimes. I had one die back, but sent out suckers and the suckers are now taller than the top growth that died. The dead growth will be removed. I grow 175 crape mrytles, lost 17 the first year from drought and mis-use of herbicide spray, but none since. They are very hardy plants. I had one that was five years old and eight feet tall that broke in a storm, it has since sent out suckers, which I will allow to grow to replace the eight foot tree. Another one was transplanted after about three years, and in May when the others greened up, this one did nothing until well over a month later, well into the summner. I hope this helps.

deja vu? Here is a link that might be useful: Same Question / Different Thread

Some kind of canker of maybe verticillium? I haven't a clue as to what diseases these things are prone to. They don't really grow here. I've had some for about 10 years in-ground, that grow as die-back perennials, and I have some potted ones I've bought in the past couple of years.

I use Maxicrop's liquid seaweed religiously when I transplant anything. I'm sure there are other comparible products. It is a foliar feed that works wonders on plants that are going through shock.