Upgrade from 8.5.16 to 9 keeps crashing

Having issue upgrading from 8.5.16 to 9. Keeps crashing on installation and get the following error.
octrine\DBAL\Exception\ForeignKeyConstraintViolationException thrown with message "An exception occurred while executing ‘ALTER TABLE expressentityentries ADD CONSTRAINT FK_B8AE3531AFC87D03 FOREIGN KEY (exEntryEntityID) REFERENCES ExpressEntities (id)’:

SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (developkasonindcom.#sql-b80_a5ef, CONSTRAINT FK_B8AE3531AFC87D03 FOREIGN KEY (exEntryEntityID) REFERENCES expressentities (id))"

Hey, just told this story to may team mates :slight_smile: Is it possible that the collation of the two coloumns are different. Check them on table ExpressEntities coloumn exEntryEntityID and table ExpressEntityEntries coloumn id, are they the same? if not change them to the newer one with the concrete cms cli command concrete/bin/concrete5 c5:database:charset:set utf8mb4_unicode_ci.
Otherwise could also be a problem of case sensitiv, cause your table expressentityentries is written in lower case only. This mostly happens if you got the DB from a Microsoft enviroment.