I don't think that it can be a result of too much salt. If you are using commercial yeast, I think that this is a common issue. They are so active that they eat up all the food and the loaf can collapse, if the gluten structure is not strong (salt can help that too). More salt will help slow down the proofing process so that you can get a longer rise. With the wild yeast that I am using it takes a long time to get going anyway. So I would say more salt is your friend.