Strange issue with vehicle and GPS/unlocker module

Hi Everyone!

Not sure where to take this next before giving up and going to the dealership. I've got a fleet of 12 rental vehicles. We've installed these trackers and they are working flawlessly on 11 of our cars:

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These units are pretty slick. You set up your account, and are able to text message the cars to get the doors to lock/unlock, disable the starter, and see where it is parked.

For whatever reason, our 2016 Prius C one doesn't like the module. The doors will not unlock after the car is parked with the doors locked for several hours. We know the signals are getting through to the GPS unit after extensive testing.

Fortunately, the problem is 100% repeatable:
1) Park the car, lock doors with either cell phone, key fob, or door switch (doesn't matter)
2) Wait at least 5 hours - if this amount of time does not pass, the unlock commands work normally
3) Send unlock command from cell phone - GPS unit responds "doors unlocked"...but nothing happens
4) Send lock command from cell - You can hear the electronics firing inside the door, re-locking the already locked door
5) Send unlock command again - Unit responds that it did something, but doors sit quietly locked

For some cars, our GPS installer shop has had to put a "double pulse" unlock module to send two unlock signals sequentially. Even after installing that add-on, the symptoms of the problem remain the same.

So, based on behavior, we're theorizing that the Prius is rejecting the electrical unlock command (even though it comes twice) after sitting idle for sometime. Is this some kind of battery protection in play? We know the GPS module is acting correctly, as we've swapped out the "brain" already with the same results.

Since the installer is ready to give up, do we take this into dealer, or try to find a different professional? Thanks for any help or insight, this is causing our renters some unnecessary stress when picking up the car!

 

Good thought, except that we can hear the signal coming out of the box to the Prius C doors. To boot, this system works without issue on our standard 2013 Prius II.