Too much salt can also inhibit the yeast. Don't add more than 1 tsp. Your next problem is with heavy loaves, or with sinking during baking. The machine provides a standard environment, and the folks who package the flour for the mix are probably careful to check how much moisture is in the flour. The recipe is trying to allow for the dry flour of a baker in Arizona, and the humid flour of a baker in New Orleans.
Humidity varies with storage and milling conditions.
If the loaf drops during baking or just before baking, it means the yeast is doing just fine, but the gluten strands in the flour have been over-stretched, and have broken. So, a loaf that sinks like that needs just a little bit less water. It is too wet. Do the same thing you did to get that loaf, but cut the water by a Tablespoon or so. If it seems to sit in the bread machine and hardly rise at all, or come out like a rock, it may not have had enough water.