this is common fault, mine does it (2000) and there are several others that have or have had this issue.
Cure is to replace the outer door handle.
Mine is intermittent, I just push on the door from the outside a little, and it always seems to open.
I have an extract from the haynes manual as to how to replace the handle if it will help, but it is from the Mk1 ulysse, not the Mk2.