MATLAB: Problem with mod command

modnot workingpausesprintf

Hi everyone,
I am running a 3d simulation of a concentration profile in a 1m^3 box with a sinkterm. I have added a line: if(mod(t,x) ==0) to update the plot for a certain time interval due to computations becomming to difficult to run for my pc. However, for x > 0.3 my 3d simulation will not display anything. Another problem I have encountered is that the frequency with which the simulation is updated changes. First it updates very fast, but as the simulation is running the update interval changes as displayed in the images. It seems like there a factor 4 with which the interval changes.
clear all
close all
%paramters
diff  = 4.058*10^-5;
%dimensions
Lx = 10;
Ly = 10;
Lz = 10;
Nx = 21; Nt  = 400000; %amount of iterations
Ny = 21;
Nz = 21;
dx = Lx/(Nx-1);
dy = Ly/(Ny-1);
dz = Lz/(Nz-1);
%CFL conditions, determines how big dt should be for the equation to
%converge
c = 1;
C=0.05; %C<1
dt = dx*C/c;
%field variables
cn=zeros(Nx,Ny,Nz); %concentration
x=linspace(0,Lx,Nx); %xdistance
y=linspace(0,Ly,Ny); %ydistance
z=linspace(0,Lz,Nz); %zdistance
[X,Y,Z]=meshgrid(x,y,z); %defining 3D grid
%Value of Diffusion
K = ones(Nx,Ny,Nz)+diff;
K([1 end],:,:) = 10^-15; %insulated problem which means that Diffusion is almost zero at the boundaries end does both sides
K(:,[1 end],:) = 10^-15;
K(:,:,[1 end]) = 10^-15;
%initial condition
cn(:,:,:) = 0.15*10^-9;
t=0;
for n=1:Nt
   cc = cn;
    t=t+dt; %new time
     
    %New temperature
for i=2:Nx-1
    for j=2:Ny-1
        for k=2:Nz-1
            cn(i,j,k) = cc(i,j,k)+dt*(K(i,j,k))*...
       ((cc(i+1,j,k) - 2*cc(i,j,k) + cc(i-1,j,k))/dx/dx +...
       (cc(i,j+1,k) - 2*cc(i,j,k) + cc(i,j-1,k))/dy/dy +...
       (cc(i,j,k+1) - 2*cc(i,j,k) + cc(i,j,k-1))/dz/dz);
        end
    end
end
%Insulation conditions
cn(1,:,:)=cn(2,:,:); %walls


cn(end,:,:) = cn(end-1,:,:); %walls
cn(:,1,:)=cn(:,2,:); %walls
cn(:,end,:) = cn(:,end-1,:); %walls 
cn(:,:,1)=cn(:,:,2); %floor
cn(:,:,end) = cn(:,:,end-1); %roof
%sink term Filter
cn(4,4,1) = 0; 
%Visualization 
    if(mod(t,0.06) == 0)
    slice(X,Y,Z,cn,5,5,0); colorbar; caxis([0 1.5*10^-10]);
    title(sprintf('time = %f minutes', t/60))
    pause(0.01);
    end
end
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