definite 4D integration takes long time/cannot find result

I am trying to do integration of a function with 4 variables.

My function is

f(x,y,phi,theta)

and some of the integration limits are function of the outer limits.

The problem is it shows warning and keep calculating.

܀warning: quad2d: Maximum number of sub-tiles reached, accuracy may be low

Is there any mistake in my code?

Or do I need alternative other than

 integral3()

?

I also do not understand why I need to use ./ instead of / in this line

 f1 = @(x, y, phi, theta) exp(-(h-y)./(lambda *sin(theta) *sin(phi)));

I learned to write the 4d integration from here:

https://www.mathworks.com/matlabcentral/answers/77571-how-to-perform-4d-integral-in-matlab

this is my code:

clear all;
clc;
rho_bulk = 2.44; # rho_bulk = 2.44 uOhm.cm
h = 20e-9;
p = 0.5;
lambda = 40e-9;
n = 10;
w = linspace(20e-9,80e-9,n);


for i = 1:n
  # limit for theta
  p2    = pi;
  p1    = 0;
  
  # limit for phi
  p4    = @(x,y) atan(x/(h-y)) + (pi/2);
  p3    = @(x,y) -atan((h-y)/(w(i)-x));
  
  # limit for y
  p6    = h;
  p5    = 0;
  
  # limit for x
  p8(i) = w(i);
  p7    = 0;
  
  #   f(x, y, phi, theta); outer --> inner
  #   limits;              inner --> outer
  
  f1 = @(x, y, phi, theta) exp(-(h-y)./(lambda *sin(theta) *sin(phi)));  
  f3 = @(x, y, phi, theta) sin(theta).*cos(theta).^2 .* f1(x, y, phi, theta);
  
  [q1(i)] = integral( @(x) (integral3( @(y, phi, theta) f3(x, y, phi, theta), p5, p6, @(y) p3(x,y), @(y) p4(x,y), p1, p2)), p7, p8(i), 'ArrayValued',true);
  
end;