Temperature Sensors and Reliability

I am having some issues with the temperature sensors (oil and coolant) on my 914.  What happens is that over time they begin to have erroneous readings. They begin to wander down, then back up, then back down like they are a zipper.  The wandering is within seconds.

For example let me use the coolant temp.  Left side is solid at 185 degrees F.  Right side matches within a degree or 2.  Later in the flight, the right side will read 130, then 150, then 90, then 160.  This is all within a few seconds.  The reading on the EFIS (Garmin) keeps just moving up and down.  Typically it was happening with the coolant sensors but over the weekend it happened with the oil temp.

When this happens, everyone points to wiring (or connectors).  I lean toward the spade connectors.  I replaced all the connectors and all is great for about 20 or so hours and the issue pops up again.  I also have removed the connector and squeezed it a little tighter in the spade portion (not the crimp) and the issue typically clears up.

However, the issue never happens on the ground.  When at idle after landing all readings are good and stable.

Some questions I have are:

1. Is there any alternative sensor to use with a different connection style?

2. Is it a possibility that the wire is heating up enough to cause resistance and sporadic readings?

3. I am using good quality PIDG crimp connectors with the plastic crimp section.  Should I use a different style connector like an uninsulated type with maybe a soldered connection?

To me it just seems the spade connector is getting loose over time and the vibration causes the sporadic readings.  Not sure I'm a fan of the connection style.