I have a composition 7689 X 1344 and freezes after 2 seconds when I hit record. It works fine as 1920 X 1080.
I import the new 5 second video back in resolume and plays fine.
My output is in Advance / Virtual display 7689 X 1344
Resolume 6.1.2
Using MacOS High Sierra
MacBook Pro 2.8 GHz i7 / Radeon Pro 555 2048MB / Intel HD Graphics 630 1536 MB