Thank you for taking that video.
Your hose setup has three 90 degree bends: one out of your unit and to the right, one up, and one out the window. If you remove one of these bends (I recommend the upward bend), I believe you’ll see much better ventilation results.
Please let me know if this helps.
@jaz, here is the new setup (link to video below). Still no negative pressure. Like before, the fans on the window board were turned off for this test.
I also tried this with no ventilation hose, again, just to double-check that I didn’t have anything obstructing to exhaust port.
Thank you for the new video. Unfortunately, this issue is not one that we are able to solve remotely. I will reach out to you via email about a warranty replacement. I’m so sorry for the inconvenience.