Bricked after coming back from service centre [and I fixed it myself]
I reset the binary counter back to zero and flashed to stock. System status says official and binary count is zero.
Sent it back for warranty because there was a dead pixel. The store handling the warranty claim wrote "dirt stuck under glass" as the problem because they didn't believe that a dead pixel could be grey. Went back to the store to collect it, the dead pixel was still there. Finally they believed me and back it went to the service centre with the problem listed as "dead pixel". They replaced the LCD.
I got it back from the service centre today. Battery was at 10%. Apps were crashing and I couldn't open anything other than Settings. (There was an out of storage icon but I didn't realise its significance at that time.) After the battery drained, I charged it back to full. Turned it on. Stuck at the Samsung logo. Rebooted many times with no effect.
Booted into recovery and download mode okay. In recovery there was a message that there's no storage left. But reset everything back to stock before sending it in! Did the service centre do something to the OS? Did they install some huge > 10 GB diagnostics stuff?!
Wiped cache and did factory reset in Recovery. Was going to let the battery drain but tried to connect it to the charger one last time. Lo and behold it springs back to life!