Both PC’s have always been playing the game in ‘Borderless Windowed’ mode.
Sherman PC:
Before updating my drivers
I just played three games on Rialto from the Arcade menu, 1 Defense as Reinhardt, 2 Offense as Mercy. There were no freezes/crashes. This PC has played many games (maybe about 20 or 30) since the initial freeze happened with no problems on other maps in Quick Play. (Note: I accidentally had the Discord overlay turned off at the time, because I didn’t think to launch Discord when I turned on my PC)
After updating my drivers
I played 3 games on Rialto again from the Arcade menu. 2 Defense as Reinhardt, 1 Offense as Mercy There were no crashes/freezes.
(Note: To keep things consistent, I left the Discord overlay off)
I turned the Discord overlay on for the next 3 Rialto games:
1 Offense as Winston, 2 Defense as Reinhardt. Again no issues.
I followed this post to the letter:
If the problem persists or rather, shows itself again, we’ll try removing/disabling the other things you suggested. This also took quite a bit of time, so I’ll update this post later with the results from my other PC, Panther. If any freezes/crashes happen when I test it I’ll make a new post to let you know I updated this one.