That’s excellent investigation / feedback.
It’s just a shame that it’s end-users that are doing this instead of Blizzard.
EDIT
Did some 2-man runs this morning…
Me on WW/Rend Barb, Other on Frenzy Barb, GR119, Not recorded
Me on Frenzy Barb, Other on Necro, GR122, Recorded
Me on Frenzy Barb, Other on Necro, GR123, Recorded
Me on Frenzy Barb, Other on Necro, GR124, Recorded
Me on Frenzy Barb, Other on Necro, GR125, Recorded
Neither of us were in a clan, so no clan chat stuff to cloud the issue. The only difference between the first run, which didn’t record, and the subsequent ones that did, was the heroes we were on. I guess it’s possible that when we went back to hero select, that might have changed which server we were hosted on when we went back in.