The problem lies with the listview. This could help:

Problem 4: When changing fields in the editable list view which have an on change microflow connected, the whole list grid is refreshed

Solution: This was the hardest problem and we had to restructure the screen completely. Basically the problem lies with the Mendix listview. Whenever changing something, the whole grid is refreshed. So instead of just an editable listview we created a dataview below the grid which looks like just another row. This dataview has the function to add new rows. As we don’t want to confuse users with a default extra row to add new rows, we preload the dataview with the last row or the list view and filtered this last row from the listview. Now we can add records from a dataview which doesn’t have losing focus problems, because that’s a problem with the Listview widget.

Source: Creating complex screens with Mendix which are user and keyboard friendly