Why is the bag being sucked into the Dust Deputy Bagger through the metal grid?

First, you’ll want to double check to make sure everything is installed properly. You can also try placing something in the bag to help hold it down. Ensure that the bags you are using are 4 mil thick. Beyond that, the main cause of this issue is typically above-average static pressure through the system. To alleviate some of this pressure, you could include an open wye, blast gate, or elbow with a valve in your setup to give the vacuum more air through another source. Always avoid dead-heading (blocking the vacuum's hose on your system).