Hi guys.

For the last few months, I receive a few times each week alert about duplicate entries in the db:
[INSERT INTO ost_thread_referral SET thread_id = 20874, object_id = 1, object_type = 'D', created = NOW()]
Duplicate entry '1-D-20874' for key 'ost_thread_referral.ref'<br /> <br />

[INSERT INTO ost_thread_referral SET thread_id = 20891, object_id = 1, object_type = 'D', created = NOW()]
Duplicate entry '1-D-20891' for key 'ost_thread_referral.ref'<br /> <br />

[INSERT INTO ost_thread_referral SET thread_id = 20890, object_id = 1, object_type = 'D', created = NOW()]
Duplicate entry '1-D-20890' for key 'ost_thread_referral.ref'<br /> <br />

[INSERT INTO ost_thread_referral SET thread_id = 20876, object_id = 1, object_type = 'D', created = NOW()]
Duplicate entry '1-D-20876' for key 'ost_thread_referral.ref'<br /> <br />

[INSERT INTO ost_thread_referral SET thread_id = 20839, object_id = 1, object_type = 'D', created = NOW()]
Duplicate entry '1-D-20839' for key 'ost_thread_referral.ref'<br /> <br />

[INSERT INTO ost_thread_referral SET thread_id = 20837, object_id = 1, object_type = 'D', created = NOW()]
Duplicate entry '1-D-20837' for key 'ost_thread_referral.ref'<br /> <br />

[INSERT INTO ost_thread_referral SET thread_id = 20827, object_id = 1, object_type = 'D', created = NOW()]
Duplicate entry '1-D-20827' for key 'ost_thread_referral.ref'<br /> <br />

[INSERT INTO ost_thread_referral SET thread_id = 20792, object_id = 1, object_type = 'D', created = NOW()]
Duplicate entry '1-D-20792' for key 'ost_thread_referral.ref'<br /> <br />

But everything seem to work fine despite these errors.

What should I do?

Thank you.