Talk:Samsung Galaxy A5 2017 (samsung-a5y17lte)
Heimdall 7% issue with SYSTEM
[...] since heimdall freaks out about the subpartitions in SYSTEM and won't move past ~7%.
Not that it changes anything about the current workaround, I don't think it's about the subpartitions.
I can observe the same failure, probably not coincidentally at 7% also with Mobile NixOS, which does not use subpartitions. The failure happens with a raw ext4 filesystem partition too.
Have a look at this: Troubleshooting#Heimdall:_Flashing_fails_at_7.25