Overleaf: Package pdftex.def error: File '...' not found: using draft setting

Because the answers to similar questions do not seem to work for my case, I post my question here:

I am currently writing an article in overleaf for which I use the latex template of my university. All .tex files are stored in a folder called ‘mainFolder’, which also contains another subfolder called ‘Images’ in which I store all the images I use. I am trying to load a .eps file into a figure as follows:

begin{figure}[H]
centering
    begin{subfigure}[t]{0.45textwidth}
        includegraphics[width=textwidth]{mainFolder/Images/image1.eps}
        caption{}
        label{}
    end{subfigure}
    hfill
    begin{subfigure}[t]{0.45textwidth}
        includegraphics[width=textwidth]{mainFolder/Images/image2.eps}
        caption{}
        label{}
    end{subfigure}
    hfill
caption[]{}
label{}
end{figure}

Unfortunately, I always get the error: "Package pdftex.def error file not found using draft setting". Minimal working examples with the same structure also work for me, so I do not know where I go wrong.

My included packages are:

usepackage{graphicx}
usepackage[outdir=./mainFolder/Images/]{epstopdf}
usepackage{todonotes}
usepackage{float}
usepackage{caption}
usepackage{subcaption}
usepackage{amsmath}
usepackage{amssymb} 
usepackage{booktabs}
usetikzlibrary{calc,angles,quotes,arrows.meta}
usepackage{tkz-euclide}
usepackage{pgfplots}
usepackage{optidef}
usepackage{algorithm}
usepackage[noend]{algpseudocode}

Adding ‘[outdir=./mainFolder/Images/]’ to the epstopdf package inclusion was proposed as a fix to similar questions, but does not work here. Neither does leaving it out, or changing it to ‘./’ or ‘./mainFolder/’.

I was wondering if anybody had encountered the same problem, or knows how to find out where the error comes from in this particular case. Any help is greatly appreciated!