I've been using Loopback quite successfully, and in fact it saved the bacon when Google screwed the pooch (they've been doing that a lot lately) on their hangout software, allowing me to route a subset of my Scarlett 6i6 to the input of the hangout (I do this on Skype as well).

Yesterday I was recording off a hangout using Reaper with a Loopback passthrough device, with no apparent issues (I monitor the loopback via headphones), but later found that the last few minutes were horribly distorted. The distortion built up over about one minute until it was intolerable. Ouch. The local recording of my own voice I was simultaneously doing on a separate track was fine.

Is this possibly a Loopback (latest version) bug, or is Reaper (latest version) doing something weird? I never had these problems on El Capitan.