Thanks a lot for your time,
I have to deeply apologize on my end as I finally figured out what was wrong :
the images url list (arround 8k) that was being used was not fully completed during the data generation (arround 4k only)
hence the recipe would call undefined instead of a proper https://link-to-img, which explain why no more
image where shown after a certain point in the PDF.
After fixing the data to contains proper url I could generate correctly the whole PDF with all the images as it should be.
The good point for us in this process is that we could find out about how chrome-pdf would handle this case and we are quite hapy about it since we still get a PDF at the end. The bad point is that it took too much time for both of us and I do apologize again for that.
Thanks a lot for your help!