Map redeploy not working

Here is the scenario:  I have an msi from the solultion that is working just fine.  But, when I pull up the solution and make a single change to the map, it works but a ton of the other field mappings are lost!  The field mappings that stop working are not ones that I even touched.

What the heck is going on?

I continue to have mapping issues where changes I make do not take effect.  This continues to be one of my biggest obstacles.