Do you have any screenshot to help explain the Illustrator problem? Based on our test, the strokes seems to be fine.
Viewing post in Suggestion - please add backlight definition option
I managed to solve the problem, it seems that the strokes were in pixel 1, when exporting with very high resolutions it ends up being almost invisible, sorry for taking up your time.
About exporting in batch mode, is it normal for it to take time and sometimes even to crash the program giving a high use of ram memory?
Note: I have an Octa Core and 16GB RAM