W-124 Fuel gauge problem

[rws11@comcast.net]

I have a 1995 E300D. 464xxx miles. Fuel gauge works perfectly until it reaches 1/4 tank. At that point it acts erratically, goes to empty, (as if the power were removed), goes back up to show level.
Once the tank is refilled, works normally again.
I have replaced the sending unit, I have replaced the pod in the instrument cluster with the gauge..... twice.
Any input would be greatly appreciated.
Richard