Hi @Joyce,
thank you for your reply! I actually found out what the issue was.
Here the problem and the solution:
In the path (for the partial update), I used the bind function of the no-code workflow builder and selected the array that I want to update. I didn’t realize, that I just need to provide the “relative” path from the variable that i selected to change the value. So basically I used, in my case, as the path: “BookingObject.items” instead of just “items”.
Hope this makes sense and helps if somebody else runs into the same issue and is looking for an answer. 