KeyError on additional processes while using Distributed

I am new to using Julia. I am trying to solve an EnsembleProblem using EnsembleDistributed() option in DifferentialEquations.jl. I have created multiple processes using:

using Distributed

I get the following error:

ERROR: On worker 2: KeyError: key (0xbf15578b, 0x9f07237e, 0x8034bd61, 0xd9f77e95, 0xf00aa3dc) not found

I could reproduce the error using remotecall_fetch(solve, 2, prob, QNDF()).

I understand that this error is thrown when the inquired key is not found in the dictionary. But what are these hash codes (e.g. 0xbf15578b) ? (I am not sure if they are called hash codes). Is it because some modules/packages are not loaded correctly on the additional processes? However, I made sure that all functions and modules needed to define prob are available on the workers by calling @getfrom 2 prob. The ODEProblem prob being solved uses custom modules.

The test example is working as expected.