Just saw this on mobile in the beta app (1.21.2 build 215) android 9 on a pixel 3 with july patch.
In this thread I'm only seeing the first and last message on mobile. Desktop works fine.
Restarting the app does not fix the issue.
I'm not at home right now so can't look into it a lot but will check tomorrow if there's anything else I can find out.
Attached two screenshots.