Playing an Arena EoE quick draft on a PC. My opponent had milled me to zero cards with Space Time Anomaly, but in my upkeep I played Nexus of Fate, shuffled it into my library and drew it again. Then I attacked with all my creatures and made sure to check off "stop at my upkeep" again. But after untapping I lost immediately anyway.
My expectation was to cast Nexus of Fate on every upkeep until my creatures brought in the win.
The attached image is a screen shot from after I lost.
The bug is either with Nexus of Fate or in the way Arena handles the "stop at my upkeep" check mark. Maybe "stop at my upkeep" doesn't work on extra turns?
I have not tested any work-arounds, but I will try switching to full control [Ctrl] the next time I need a stop on my upkeep instead.