Yes, type mismatch is common. Its in the CSV files which are just text. You can work with them through a decent text (i.e. not notepad).
Once you find out what is causing it, you want to make the fix in your league file so you don't get the bad data anymore. Otherwise you would have to make edits to your CSV files after every season before you do the CATO processing.
CATO is very great, but very fragile.
A quick search of this forum will show you that your are only one of many having difficulties.