I've mostly reproduced this, but am stuck at one point.
On your file if I open Filter1 - Filter3 they are configured for "Get choices from fields in this form" but the "Entries" section is blank. I get an error even if I click "OK" on the sample, yet is works in demo mode.
Obviously I am missing something with the proper way to configure this, and it's an important part because as it is now each Filter level displays every entry in that level. In other words, right off the bat everything designated as Level 2 and Level 3 is visible in their respective drop-downs, irrespective of what is selected in Level 1.