The sim will not allow me to sign a player to a team that has less than $0 using the Manual Free Agents dialog. Even when the signing bonus is $0, I get an error that says: TEAMNAME doesn't have enough money to sign this player because of the bonus. Teams with less than $0 must be able to sign new players otherwise our league will fall apart
In order to get around this bug I have to stop my process of signing free agents, go to the Unassigned Players dialog, add the player there, then go in to the team, the roster, then the player and manually set the contract. It is a bit annoying to have to do all these steps.