DB Error: Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation '='

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Dear friends,

After upgrading OJS, I try clicking in review, unassigned, in editing there is error like this :

DB Error: Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation ‘=’

How to solve ?

Thanks