Future Committing W line types

Hi, I'm having trouble with future commits and W line types.

Scenario:

1. SO is entered with a W line type and date is pushed outside of commitment window. Item is future committed in Availability

2. Date on SO line is manually changed and moves within window and item will no longer be future committed

3. As soon as you change the date, the branch/plant field clears out and we get a Branch Invalid Error because it's blank.

Is there any documentation or explanation for this issue? Thanks!