Getting "Invalid Input" error when clicking "Save & Publish" when trying to update a policy

WMS version 4.3 HF1 286

Like the title says I'm getting an "Invalid Input" error when clicking "Save & Publish" when trying to update a policy. Even if I open a policy and make no changes and click "Save & Publish" I get the same error.

I'm logged in as administrator. Nothing has changed in a long time but now we need to change the Citrix Broker server.