I may have an idea, this happened to my grandfather brother. He was with his unit in the pacific. Was injured/ wounded and was taken to ship hospital, the unit had moved so far inland by the time he had healed two months later the combat unit he was with were to far inland for him to be brought back up with his unit would take too long. They than attached him to a replacement unit or battalions which was used to by commanders to replace wounded or killed soldiers on the frontlines. It may have been possible your relative was injured, sent to replacement unit because is originally unit was already to far inland this transferring him to a replacement company. This is just my theory based on actual events with my grandfather brothers ww2 service. Maybe you can find the Morning report showing this transfer, if he was wounded it may be an army hospital morning reports transferring him to a replacement unit. Check all your angles
Hope this helps, good luck with your search.