I am NOT an expert on this problem, just throwing out an idea.

Do you know what a "driven sand point well" is?

Basically, you attach a strong screen with a point on the bottom to some steel pipe. You then hammer or pile drive the steel pipe into the ground until the screen at the bottom reaches the groundwater table. At that point, you run a pump inside the pipe and have a water well.

You might be able to use that process to evacuate the water on the wrong side of your liner.

Drive a vertical sand point well beside your pond, or if there is a dam or low side, then you could drive the pipe in horizontally.

If you have much lower ground nearby, you might be able to start a siphon and remove the water outside of the liner. If no low ground, then you might just be able to attach a pump and de-water the area around the liner as needed in the future.

Good luck on getting your pond fixed!