Why do I get a concatenation error when I try to use the remote parallel server?

I'd like to use a remote Parallel Server to execute my code. I have a main script, that calls a function embedding a parfor loop. When I run this script on my computer, everything works smoothly. However, when I try to use to remote Parallel Server, I got the error

Error using parallel.internal.pool.FileManager/addAttachedFiles
Dimensions of arrays being concatenated are not consistent.

A minimal working example is

myCluster = parcluster;
parpool(myCluster, 'IdleTimeout', 180);
parfevalOnAll(@feval,0,@ExternalLibrary);
myfunction;

where ExternalLibrary is a function of an external library that loads some files in memory, and myfunction is a dummy function

function myfunction
parfor l = 1:10
    for k = 1:5
    end
end
end

I noticed that when I copy and paste the code of myfunction inside the main script, I do not receive the error.

Why do I get this error and how can I solve it?

[Alvaro]

Could you try attaching the function file to the pool?

https://www.mathworks.com/help/parallel-computing/parallel.pool.addattachedfiles.html