I'm pretty savvy at appliance repair but I'm not an expert. I've repaired bad boards, diagnosed and swapped plenty of parts, and more. But this one has me stumped.

Our 11 year old Whirlpool Duet washing machine has been pretty good. A few weeks ago the pump went out. NBD, I used the internal diagnostics mode to determine it was, in fact, the pump. Got a new pump and first load worked fine. But now, intermittently, the washer over fills and starts leaking. It's not every load, just occasionally. But leaks from a washing machine are not ok.

I've watched it through a cycle and it's like the sensor is telling it that it needs more water mid-cycle so it just keeps adding more. It will start the cycle normal, water coming on the shifting off, and drum/l starting to tumble. Then while it is tumbling the water will kick on for a bit, kick off for a bit, back on for a bit, back off, repeating several times while the tub is going through the processes for washing.

Any advice?

Water inlet valves sticking or the fill switch/hose is dirty/plugged.

Or has mineral deposits built up on it.

A sticking inlet valve will turn on/off/on/off multiple times during a cycle?

You can either have a bad coil  losing continuity, you can have a bad fill switch that isn't reading correctly, you can have a clogged inlet screen that keeps making the machine try to add more water, you can have a plugged water fill switch line that isn't telling the board to stop filling. I'd start with the fill switch/hose as that tells the board there is enough water in the tub.

You could have a bad relay board also. The actual touchpad/control is likely fine if you can control it.

The water inlet valve is a common failure point on the Duets.  Enter the washer model number into Amazon and you will get a selection of inlet valves, priced from $15 to $60.  I settled on a $30 valve and it's been fine.  Always replace the filter gaskets on the filler hoses.  You may have them on both ends.