At this point, I believe you have tried all the obvious troubleshooting for your issue. There doesn't appear to be anything else wrong from your log.txt.
From earlier posts, you figured out the lines were associated with HDR rendering, and you have submitted a bug report. Please note you will most likely not hear from the developers. For now, your best bet is to turn off HDR mode and check for release notes when 10.50b1 comes out later to see if a fix is included.