Android TV runs out of space watching a recorded program

I installed the Channels app on my parents’ Android TV so we could watch a recorded program on my Channels DVR (I have site-to-site VPN setup, this was not an issue, the recorded program worked flawlessly from my iPhone). The problem is my parents’ Android TV only has 4.5 GB of storage, about 1.2 GB free. The Channels app took about 87 MB initially. After watching the recorded program for 10 minutes or so the device ran out of space and shutdown. After that the app wouldn’t connect to the DVR. I went into the Android settings and saw to Channels app now taking up 1.2 GB. I deleted all the data for the app. Now the app works again. I changed the play back settings to stream at 4mbps. Now we can watch the recorded program for about 30 minutes before storage fills up.

What’s taking up all the space? Is the client buffer >1GB, even at 4mbps? Is there a way to limit the client buffer for recorded programs?