Pond almost full and leak halfway up the backslope. Doesn't say how many feet of elevation delta we're dealing with here, but there could be some hydraulic pressure on the leak path. Reducing water level will reduce leakage and could save the dam.

I second the suggestion to drain pond some. If your pond has a valved drain line, use that. If not, a siphon system. I successfully built one with flexible hoses (4" & 6" 100' long are cheap) but the "up and over" from water level to max was just 2-3'. If more than that, you may have to go hard pipes, T fitting with a removable cap to fill on top (lotta Youtube videos). If nothing else, get a pump and pump it over the dam.

You're better off losing water than a dam. Don't need to drain all the way, just down to where leak is. Get your builder out there. If they do any work, they'll want to drop water level anyway.