Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
There has been a service bulletin for that type of concern. Here is what it states.
2002-2006 MPV - POWER SLIDING DOOR (PSD) RE-OPENS AFTER STARTING TO CLOSE AND LATCH
After pressing any Power Sliding Door (PSD) switch, or manually pulling a rear door to close, the door may re-open fully after trying to close and latch.
Customers having this concern should have their vehicle repaired using the following repair procedure.
Rear door rubber wedges may be out of alignment causing the PSD control module to detect a load and re-open the door. To prevent this concern, perform inspection below.
B-Pillar - Rear Sliding Door Contacts Replacement