As the coolant heats up, temp sensor 1 will trend towards 0.5 volts. Temp sensor 2 will stay cooler (higher volts) because that‘s the cold side coming out of the radiator. So the general trend looks okay. Right after starting, you’re already putting some heat into the system, which might explain why sensor 1 is lower than sensor 2. I’d check them dead cold before starting just to make sure they’re about the same, since that’s when you are having an issue. If they are about the same, I think you can rule out the temp sensors.