From the description, the behavior is normal and expected. The DC Loads is a derived value, and its sign indication of the direction of net power flow. (In this case + is flow to the loads, and - is flow from the loads.)
In this image, the AC Charger is a Smartshunt monitoring an external charger putting out 75A (4kW).
DC Loads represents (+) current drawn by (non-Victron) inverters, and the (-) current from the charger.
Note the charging power flowing into the battery. It is the sum of Solar charger output, AC charger output, less power consumed by the inverters (920W).