It does not matter if it is actually done every week, or as a calculation of your investment by the end of the season. the outcome is the same.
I think that players (4 per each week of 40000$ investment) will be chosen randomally for the scouting, regardless of prior scouting, unless they were already scouted twice and they are not candidates for the randomal choice any more.
It would make more sense if better players would be chosen for a second scouting, yet it seems to be totally randomal.
Still, I have no real knowledge, only assumptions...
:(