Q: Is sku grid changing the handling time of my amazon listings?
A: Be sure you have not left the default handling time in your settings blank. Amazon requires it in their data feed, so even if you leave it blank, Sku Grid has to default to a value. And even if it doesn't, then Amazon would change it once the items post (It is possible when Amazon automatically does it, they set it to 1 or 2 days).
So set a default value for default handling time and if you have individual items that you want to be set differently than your default, you edit them in the grid and set the Default Handling Time on the individual item to 1 for example.
When adding items into the grid, make sure that if the handling time you need is different than what's in your settings, that you set it on that item as you add it into sku grid. And if you change your handling time on amazon for an item, you would need to edit the item in Sku Grid and change it there also.