Hi @e-smartsolution,
OJS intentionally uses an index collision to check whether a value is already created there. If there is, it uses it; if there’s not, it creates one. It seems that some database servers are now starting to complain about this where they previously did not; you can change the behaviour to avoid this by applying this change: Avoid index collisions if possible · pkp/pkp-lib@b193290 · GitHub
See also: DB Error after upgrading to OJS 3.2.1.1 - #5 by Tarcisio_Pereira
Regards,
Alec Smecher
Public Knowledge Project Team