Fleet doffs cannot be used to starbase contributions. Yet, they can be listed on the exchange. Since there is sometimes no way to tell the difference between a 'regular' and a fleet doff, this is going to lead to lots of complaining and bug reports of 'doff contributions not working' when really it is working as you have intended. Either reverse it back to where you can contribute them, or make it so that you can't list them on the exchange. Or, somehow mark them as 'fleet' so people can tell the difference.
Come join the 44th Fleet.