I'm wondering if it is leaking past the seal around the shaft, or around the seal at the case. If it's around the seal and seal with some sealant on it should help. Check the bore the seal rides in, maybe it was damaged when they removed a seal. A small gouge could be a path for fluid to leak. Some transmissions have an o-ring in the shaft bore. If a shop could go in the bore and cut a grove for an o-ring, that would keep most all the fluid from getting to the seal.