viper 791xv randomly not unlocking

On my 2003 Mazda6, I installed my VIPER 791XV over two years ago. It worked flawlessly for about a year and a half, but now 50% of the time when I disarm the alarm, the doors do not unlock. I already replaced the relay and it did the same thing, so not a sticking relay. It doesn't seem to matter what sequence of events occur or weather or anything, it's totally random. Is this a brain issue? If so, where and how much is a new brain?

All connections were soldered, so loose connection shouldn't be possible. I haven't tested it yet as it is pretty far up in the dash and I'm not looking forward to the experience.

The best thing to do is meter the the unlock wire going into your relay to make sure that you signal coming from out of the brain. If 50% of the time you have no signal, I would say it is the brain. If you always have signal but it still wont unlock then you need to look further down the line. It looks that car uses resistors for both lock and unlock. It is possible that maybe the connection on the resistor is broke or loose. That is what I would check next.

the resistor is only on the lock, not unlock. One thing that is odd is that the alarm has never once failed to unlock my car when the ignition it turned to off. I'll check out the connections as soon as I can.

Your right on the resistor thing. I just glanced at the tech sheet and saw multiplexed on the lock/unlock. So do you have a relay on the unlock side or just the lock side?

You may need to check the wire, too.  Make sure it isn't getting pinched in anything.

there are two relays, one on each. They are easily accessible, so I can do my testing there.