You've clearly demonstrated that power is getting to the tabs and that ground is also okay otherwise you wouldn't be seeing voltage between the two tabs. Odds are the problem is at one of the tabs, either corrosion at the tabs or separation from the grid. If it's not visually apparent which side it likely is then you can try carefully probing for voltage in an area of the grid closer to the tabs with a sharp needle connected to your meter. It may take a little practice to poke through the protective coating to get enough contact for your meter to see it momentarily. Choose a wide area of the grid where a little scratch won't matter.

Knowing that the left (driver) side tab is connected to +12V from the defrost switch (I determined that from wiring diagrams, you can confirm with your meter) and the right side tab goes to ground and that your testing has shown that wiring to the tab connectors is okay allows you to proceed as follows:

o Connect one of your voltmeter test leads to a good chassis ground (you can use the right side defrost tab if that is convenient).

o With the defrost switch ON, try probing with the needle into the grid near the left (driver side) tab. If you don't see any voltage there (but still do at the tab connector itself) then that tab is your chief suspect.

o If you do see voltage there then try probing into the right side of the grid. If you still see a bit of voltage over there then that confirms (at least some of) the grid is okay and the problem is likely at the right tab.

You should then try to confirm your diagnosis from the opposite side, with your one meter probe still on chassis ground. With the defrost switch off and your meter now in its most sensitive milli-Ohms setting:

o Try probing into the grid at the right side. If you see a hint of meter action then that suggests the right side tab is okay. Probe over on the left side of the grid and if you still see a bit of continuity then that confirms the grid is okay and it's likely at the left tab.

If attempting to clean up the electrical contacts at the tabs doesn't help then there are kits made by Permatec and Loctite for grid and tab repair. Some people have more luck than others with these kits. Do a bit of research online and learn how to best use these kits and do those repairs. There are a number of good YouTube videos.

I once tried repairing a couple of broken fine grid lines with the special conductive paint and had no success, probably because the resistance through the repaired path was still much higher than through the other intact grid lines. I also may not have done a perfect job of prepping the surface, but at the time I thought I did.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now