I've had this happen a couple times on my metal press. I have several excavators, a crusher, and the metal press all attached to an HV power grid powered by a single diesel generator. If I shut off all the machines or if I leave them on but all of them are idle, the generator will occasionally keep running.

I isolated it to the metal press but I may have seen it happen on one of the excavators. The metal press is sitting idle after previously running some press operations. I have also tried flipping the redstone signal to disable the machine.

If I cut just the wire to the metal press, the generator stops. If I hook it back up, the generator starts running again. If I break the metal press, the generator stops. When I recreate the metal press, the generator remains off. It's acting like it still thinks it's running and pulling power from the grid even though there is nothing going through the metal press or even if it is disabled manually. Doesn't go away until you break the machine and create it again.

Minecraft 1.14.4
Forge 28.2.5
Immersive Engineering 0.14-95

You can use the Current Transformer to read how much power is flowing.

Also happens occasionally with generator hooked up to bank of HV capacitors. Nothing being drawn out of capacitors and they all show full charge but generator will occasionally keep running until you cut the input wire to whatever cap decides to keep pulling power from the grid. Keeps doing it until you break and replace the capacitor.

I've been so far unable to replicate this.

Do you have a minimal setup in a creative world that can produce this issue?

Unfortunately, no. You can probably close this anomaly since it's going to be very difficult to duplicate. If I can get it to happen again, I'll try to gather more information. It's acting like it has a very small amount of remaining power that needs to be filled that isn't getting zeroed out but I haven't looked through the code to see what it might be doing.