If you are getting irregular DOOR OPEN warnings....then one of the door monitors is probably having issues...and I would suspect it as the reason for the false alarms before the hood sensor. I would discount the hood sensor...but would investigatemoreinto the "door open" warnings which is a definite indicator that something is wrong if the doors are actually closed.
You can also check the DWA (anti-theft alarm siren system) red LED flash status. When you arm the vehicle (by using the remote key buttons, or locking the vehicle using the driver's door exterior lock) the DWA is armed and the red LED should indicate the system's status (see chart below). If the LED is flashing rapidlyy for 10 seconds...the there's an issue with one of the DWA monitors...and again,since you have a "door open" warning when all the doors are closed...one of the door monitors is probably the culprit.
You can lock the vehicle without arming DWA...but you have to kind of think outside the box. Using any of the door lock pins or the central locking system button on the center console...will single-lock the vehicle and NOT arm DWA. But you must work around the driver's door which has an anit-lockout feature which requires the driver's door to be closed in order for it to lock. Thus, you must close the driver's door first, then proceed to manually lock all the doors...or use the central locking button...but again, you must be using one of the other passenger doors to do either of the locking routines aforementioned since neiither of those 3 doors have the anti-lockout feature. You should still be able to use your remote key to unlock the vehicle.