I am working on Mac 10.15.6 & Seemusic 4.3.1. Video render hangs right after audio rendering is done. It sits there with very high CPU activity. Any possibility you provide the older version (4.2) available for download until you fix the bug? -V
I'm not sure yet.
Please try rendering the Transcendental Etude no. 12 Chasse Neige from the actual Sample Pieces list - not the media overlayed on your piece.