NOC mismatch in GCMS notes

Hello everyone,

I just received my GCMS notes and I see that my application has been flagged for refusal because one of my work reference letters doesn’t match the NOC I choose. For context, I got 3 reference letters from 3 places I have worked, the other 2 were fine but 1 was flagged as a mismatch. All experiences are in the same industry, the difference is that for the one flagged as a mismatch, that was my 1st job and my responsibilities were limited but progressed overtime as I grew in the industry and moved to other organisations hence my other reference letters were more fitting to the job description of the NOC.
I’m really confused on what to do next, should I choose a different and more fitting NOC for the one flagged as a mismatch or should I get a more elaborate job description that fits my chosen NOC and accompany it with a letter of explanation.
Please who has been in the same situation before?
What did you do about it?