Insert update step is only inserting to mySQL

Hi guys,

I use DI now for quite a while. Now after a lot of scripts with Oracle and MS SQL I needed to load data to a mySQL database and update them later.
I used the same script I used on MS SQL and Oracle with a insert / update step and this updated the data perfectly - but not on mySQL there it always created new database entries.

For me it looks like the lookup step is not noticing that the dates are the same, but they are, coming from a csv file.
The inserted data is producing duplicate DB entries which are exactly the same, instead of updating them.

Any ideas?