Marc's case was a very different one, so I doubt your unit is bad.
When we see oil temp problems, it is almost always a mediocre ground between the engine and the airframe. The oil temp sensor is very sensitive, so a few mV of error is noticeable.
When in flight, your alternator is the thing powering the plane, so all the current in your plane goes through the ground connection from the engine to the airframe. If this connection is resistive at all, there will be a voltage drop across this (Mr. Ohm was right!), and this voltage will add to the voltage that the EMS sees for the oil temp, causing an error. Given that the load in an airplane varies, so will the oil temp.
We've seen this caused by painted engines and thus painted ground lugs, painted airframe grounding spots, frayed cables, and just small cables. It happens more on composite planes than metal ones, but it happens everywhere.
Let's get your grounding problem fixed, and see if that helps your amps as well. If it doesn't, then we'll look at that once we get the oil temp stabilized.
