We have determined that one of the plates for the sealer heads did not ensure that the jar lid was exactly centered on every jar. This caused the uneven heating, which caused the brown coloring inside the lid. We have discontinued the use of this plate until it is machined for an exact placement.
We have tested the gel that was returned, and found the viscosity, ph, and conductivity to all be within our acceptable range.
We were also able to determine that the "browning" was between the foil and the lid, so there was no foreign matter introduced into the gel.