Condensation inside wall on vapour barrier
So you are seeing water from the inside of the wall, contained within the insulated cavity through the clear plastic, right?
Congrats, you are seeing thermally driven vapor. Normal water vapor gets into the surface of the structure, then it gets heated up by the sun. This actually drives the vapor deeper into the structure. What should not be happening is actual condensation on the inside of the plastic. There should be enough insulation so that any vapor is gently warmed before it hits a condensing surface... where it will drip down, collect, cause rot and mold and attract termites.
You've got your walls open, might be time to thing about GOOD insulation. Fiberglass batts is not under that heading.