Error for multiple Constraints with fmincon

Hey everybody.

I encountered a problem and can't figure out a solution or even the exact reason for it.

I'm setting up a optimization using fmincon. I want to have one equality and one inequality constraints. I had it already working and made some changes to the constraints. Now I can't make it work again.

these are my constraints:

%Constraint function

function [c,ceq]  = conRT(in, V, depl, Fsum, Screws, Z,  A_BT, C_Stern, h_B)
myHoltropObject=Holtrop(V, depl, Fsum, Screws, Z,  A_BT, C_Stern, h_B);
Lwl = in(1);
B = in(2);
T = in(3);
C_B = myHoltropObject.calcC_B(in);
GM = myHoltropObject.calcGM(in);
deplVorh = Lwl*B*T*C_B;
ceq = depl-deplVorh;
c = GM - 0.4;   %<-- without this constraint everything is working fine. 
end

here is how I call the constraints:

constraintA = @(in) conRT(in, V, depl, Fsum, Screws, Z,  A_BT, C_Stern, h_B);
problem = createOptimProblem('fmincon', ...
    'objective',objectiveA, ...
    'x0',x0, ...
    'lb',lb, ...
    'ub',ub, ...
    'nonlcon', constraintA, ...
    'options',options);

I get this Error:

I know what this Error means. But I just can't get my head around why it suddenly popped up after it already worked. And also I don't know where I created that error.

Any advice will be geratly appreciated!

[Ameer Hamza]

Can you share other functions and variables necessary to run this code?

[Leon Stolp]

I already worked this out. The Problem was that the variable "GM" is a talbe that uses integers but was given a decimal as a input.

Thanks for your Time, anyways!