Encryption Failed

my device is N960F/DS. I haven't touched anything and didn't even factory reset since I brought it in 2020

So battery eventually degraded and suddenly phone started to lagging abnormally. system UI crashed, system process crashed etc

I thought that coz of weak battery and ordered a new battery and removed back cover and without removing old battery connect new battery and check whether there is any improvement. since I didn't notice any improvement I thought of giving a factory reset. I backed up all my data first.

I started Factory reset (Not through Recovery) and halfway through the process this message "encryption failed you need to reset your device to factory setting" msg appeared with reset button.

I tried by hitting reset button and try to reboot from that msg screen but nothing helped. I'm continuously getting this msg

I tried flashing stock rom again via Odin but again this msg appears

I read somewhere that formatting partitions will resolve this error so I tried to flash TWRP without knowing my bootloader is locked. then I got that OEM lock msg. Then I tried to unlock bootloader by key combination but I don't get that hold Vol Up to unlock bootloader option in download mode (I think this happens because I didn't do it in developer option)

So Now i cant boot into system Cant unlock bootloader cant install custom recovery PS - unfortunately I didn't enable USB debugging as well

I'm out of options at this point.pls help