I have had the same problem when I tried to write a post in Chrome app. After few sentences it just stopped writing and I could change my cursor from place to place but text didn't update. After a while waiting it did all the things I tried to do.
This is weird because I do not have battery drain on my Mi 9.
I am still using weekly 9.12.27 and not the latest one though.
SoT is around 8 hours according to AccuBattery app.
On average when screen is off I have 1,6%/h battery consumption.