Same problem with SD card playback.
Iphone SE 2 with IOS 15.0.1
Yi Home app
Yi Home camera 720p with latest firmware 1.8.7.0F_201809191400
restarted, reinstalled and formatted
After formating SD card I can only playback until midnight of the day of format.
The recording is on the SD card but the viewer displays "No video recorded to SD Card on ‘x’ " x = every day after the formating day
When I scroll to 23:59:55 on the day of formating, the playback runs also after 0:00:00 the next day, so the data is on the SD card.
So there is a bug in the app that hopefully will be fixed very soon!