Strange Primary Key Violation

[Leo Hernandez]

I have a column of values full of special characters. I'm trying to create add a primary for that columns and the command finds that there are duplicate values in that column:

MariaDB [AR]> alter table master add primary key(path);
ERROR 1062 (23000): Duplicate entry '1%03N_' for key 'PRIMARY'

But then I run this select to see which rows have duplicate values in this field:

MariaDB [AR]> select * from master where path='1%03N_';
+--------+-------------------------------------------------------+---------+------+
| path | clipid | grp | m |
+--------+-------------------------------------------------------+---------+------+
| 1%03N_ | AD0S9TT9UB8Q7e890GMTC46KBIPG417JGNM50B0E2B77QQFTKLIVJ | THGSTsf | 1 |
+--------+-------------------------------------------------------+---------+------+
1 row in set (0.04 sec)

... and I find only one row.

What is going on here??