Historically there are a lot of revolving door style career moves, but usually from the direction of active duty officers going into industry roles. And in the last decade we've also seen the flow back in reverse direction (e.g. SecDef, technically a civilian office)

While it wouldn't apply to every person serving, it seems possible to have exposure to conflicts of interest if the person's civilian job directly intersects with the industry pool where systems are being developed and procured from.