Replaced the starter six times in the last month, what is causing them to go bad?

In the last month I have had 6 starters go out on me. The first one (the original) when we took the starter apart looked like an internal wire came apart. We have since replaced the starters with refurbished ones. They all work for a few days and then all burn out. I will push to start, and I get a loud click (almost thunk) sound and then white smoke from the starter. The wiring harness has been redone. There are no issues or drainage from the battery. Any advice to check or try would be appreciated!