It seems that some of the data records do not contain a value or the value was not copied into that YYYY field you are using in table.
If I am guessing correctly, you are using a different date field in @timestamp from the table field one which you are trying to filter out
First, verify if the timestamp field in the data view is different from the one you are using in the table.
i will suggest to create the runtime field or you may use logstash to get the year from the timestamp field and save it as keyword.
follow this elastic discussion to write the script to get year out of date field