Hey there, @Louis 
Thanks for your patience here, and my apologies for the back and forth on this. I assure you we are invested in your project being successful!
I know you mentioned that your build works on vercel and not netlify-- is there a difference in configuration? If so, a good place to start is debugging your build output.
Additionally, have you confirmed that all of your versions are the same? You can use this link for more info on how to check: [Support Guide] Debugging Netlify site builds. My apologies for not sending this to you earlier.