Tanks to all for your advices.As information: thanks to a recently adobe
kb, I have found the quickfixe QF9500.17 (routes that disappear in
editor but remain in deployed workflow).After a contact with the Adobe
support and the installation of this quickfix (a workbench fix --> not
necessary to patch server), the problem seams to be solved.Ths patch
apply to 9.0.0.2 (9.5)RegardsDenis