Simscape - Number of equations exceeds number of variables

Hi guys I am attempting to model a very simple fuel tank with a pump taking fuel out at a constant rate in Simscape with custom components. The volume in each tank is calculated at each time step with a table lookup of height volume tables which are taken from the geometry of the tank, here I am simply using a cube geometry, so depending on what height the fuel is, the lookup table will give the volume of fuel for that height. When I run the simscape model I receive the error "Number of equations exceeds the number of variables". My code for the components are below;

component HVTable
   
   nodes
      Q=TRIAL.domainFuel; %Q:right
   end
   
   parameters (Size=variable)
      InitialVolume = {20000,'l'}; %Initial Tank Volume
      Height = {[0,500,1000,1500,2000,2500,3000,3500,4000,4500,5000],'mm'}; %Fuel Height
      Volume = {[0,12500,25000,37500,50000,62500,75000,87500,100000,112500,125000],'l'}; %Fuel Volume
   end
   
   
   outputs
      h = {0,'mm'}; %h:left
   end
   
   variables
      V = {0,'l'};
      flow_out={0,'l/s'};
   end
   
   function setup
   V=InitialVolume;
   through(flow_out,Q.Q_jet,[]);
   end
   
   equations
      
   V.der == -flow_out;
   h == tablelookup(Volume,Height,V,interpolation=linear);
   
   end
   
end



component BayAMBA
   
   parameters
      V={1000,'l'}; % Initial Fuel Volume
      TankSize={8000,'l'}; % Tank Size
   end
   
   parameters (Size=variable)
      Volume = {[1, 2, 4, 8, 10],'l'};
      Height = {[0.1, 0.2, 0.4, 0.8, 1],'mm'};
   end
   
 
   
   nodes
      I=TRIAL.domainFuel; % I:left
      O=TRIAL.domainFuel; % O:right
   end
   
   inputs
      H={0,'mm'}; %H:left
   end
   
   
   variables
      VolumeFluid={0,'l'};
      VolumeUll={0,'l'};
      P={0,'Pa'};
   end
 
   
   function setup
   if V<0
      error ('Volume cannot be negative.')
   end
   
   if TankSize<V
      error ('Fuel Volume cannot exceed Tank Size.')
   end
   
   across(P,I.P,[]);
   across(P,O.P,[]);
   
   end
   
   equations
      
      VolumeFluid==tablelookup(Height,Volume,H,interpolation=linear,extrapolation=nearest);
      VolumeUll==TankSize-VolumeFluid;
      P==0;
      
   end
   
end

      

component FixedRate_Pump
    
    nodes
        T = TRIAL.domainFuel; % T:left
        X = TRIAL.domainFuel; % X:right
    end
    
    parameters
        commanded_pump_rate = {0.7, 'l/s'}; % Source flow rate
    end
    
    variables
       P={0,'Pa'};
       flow_rate={0,'l/s'}; %flow rate
    end
    
    function setup
    across(P, T.P, X.P);
    through(flow_rate, T.Q_jet, X.Q_jet);
    end
    
    equations
       
        flow_rate == commanded_pump_rate;
        
    end
        
    
end


Can anyone give me help to find what may be causing this error? Any comments would be greatly appreciated.