Description:
Must provide a year_made unless the product is_made_to_order or is_vintage. Template has year_made: '...'
This means the year_made column was left empty.
If is_vintage to TRUE year_made can be blank.
if is_made_to_order is TRUE year_made can be blank.
Solution:
You need to enter a valid year into the year_made column.
A valid year means:
Whole number
Less than or equal to the current year