How are you getting your server stats ?

Analyze your tables.
select chain_cnt, table_name, owner
from dba_tables
where chain_cnt > 0

If any of your tables have row chaining in them, increase pct_free for table.

search forums on how to resolve row chaining.

If I remember correctly, you will have to copy chained rows to another table.
delete chained rows from table
copy chained rows back to table with higher pct_free setting.