What do you mean resetting to auto.  What exactly is it doing 

I pulled up your car and wanted to double check a few things. The the protocol for these types of issues is a  reset and checking fuses and relays. This is what they have listed 

First check all the fuses and relay. I tried pulling up the exact ones for you to check but the diagrams don't seem available for your car. 

The next step is to try a reset

Climate control reset 

1. Ensure your Lexus vehicle is in park.
2. Start your vehicle.
3. Locate the knob that turns on your radio/multimedia system.
4. Press and hold the knob for several seconds.
5. You’ll notice your infotainment system rebooting.

After the reboot has been completed, you should be able to utilize your climate controls as normal.

It can be a computer issue , a short or a faulty climate control. You may need someone with a fancy scan tool and experience with Lexus systems to figure it out. If you have a scan tool that has a bidirectional feature might be able to pull up the modules and find the fault yourself.

I live couple hundred miles away. If I lived in that area I would try to help you out. I'm from NJ 

First try the rest and look for blown fuses. You can try going to AutoZone and see if they have a bidirectional scan tool you can use. The parts stores usually have multiple types available. All the you need is something that can pull up all modules. There are scan tools that cost 175 that can do it. Fancy scan tool will be best and it should let you access the modules and get access to the system itself. Using a cheap one that pulls all  modules may be enough to find the cause.