Hi Laurent Burtaire,
I was checking the release information note (1818517 - EHP3 for SAP SRM 7.0 SP stacks - Release Information Note) on today and I am able to find that there are couple of notes which have been advised to be applied as part of SRM 7. 0 EhP3 SPS04.
In that, I am able to find the note (2005524 - Buy on behalf and Team shopping carts are not visible in POWL) where the same issue has been discussed.
I hope this note will resolve that concern. I will keep you updated.
Best Regards,
Bharathi