Seems the fuse block may be intended to receive power directly from the battery and converter? Perhaps the positive wire from the load terminal of the controller to the fuse block should never have been installed,
This from the FWC Operation Manual:
When the camper is plugged into 120v shore power or a generator (electricity), the silver 12v master switch can be in either the “IN” or “OUT” position to operate the appliances in your camper. However, if you would like to have your camper battery(s) recharge from the 120V shore power electricity, the silver must be pulled “OUT” to allow for recharging of the auxiliary battery through the 30amp IOTA power converter