I just encountered this error, and saw a closed post that I found in search of the answer, that had no answer, and since it is closed, I can not add to, so here is the solution.
Basically, if you are like me or @kyleandrewpittman or @gaharrington and are trying to upload a CSV with a list of something, then you need to format it as a JSON array, and not just a list separated by comma.
I had in my CSV a field that in the DB is a list of text, my CSV cell value was I'm healthy, I'm tall, I'm spirited…in order to format as an array I used chatGPT, asked it to give me the same list formatted as JSON and then to minify it, the result is as needed to enter into the csv cell value for the upload to work…["I'm healthy","I'm tall","I'm spirited"]
In the event that the field is a list of related ‘things’, use the same approach, but the values in the array need to be the unique IDs of the ‘things’.
In the event that the field is a list of options, use the same approach, but the values in the array need to be the Display values.