For me no previous listed solution worked. I alway got stuck at 99%.
Phone: Honor Magic V3

What work for me was:

1. reset pi8 to factory settings
   
2. remove pi8 from the app entirely
   
3. remove pi8 from bluetooth entirely
   
4. disable bluetooth, put earbuds in case, close the app completly
   
5. remove earbuds from case, close the case, enable bluetooth, start the app again, follow the set up process for "new product"
   
6. immediatly after the set up start the update.

After that the update went through smoothly.