We noticed that some of the data in our Columnstore tables had incorrect values stored.
We use a MyISAM table as a backup for our columnstore tables, on comparison of our MyISAM tables to our Columnstore tables we saw that some rows had values in fields shifted to the left by 1 column.
On review it turned out that rows that contained a \ as the last character in a string field had all the subsequent fields shifted left.
Our system makes changes to our MyISAM table and then does a "INSERT INTO <Columnstore> SELECT * FROM <MyISAM>" we have narrowed it down to this SQL Query causing the issue.

I have attached some example sql files that demonstrate the problem.
After Importing the SQL running the query:
"INSERT INTO testing_backslash_cs SELECT * FROM testing_backslash"
will demonstrate the issue. Notice that row with id 2 has erroneous data in the name field and all subsequent fields are shifted to the left by 1.

The query only runs successfully when columns at the end of the table have default values set.