I have a flow that is set to trigger on a monthly basis to check for empty fields in a particular column. The '@empty' function works perfectly well if I use a simple 'When a new item is created' trigger, but it does not work on an existing list where I have to use the 'Get Items' trigger:

The condition simply returns true for each item, even if that item has data. I know the '@empty' syntax is correct because it works when I use the 'When a new item is created' trigger instead.
Any ideas? I'm stumped!
Thanks