AhOh, you said FDE. Well most encrypted A12 ROMs are FBE.
You should do clean install at some point to move to FBE since I read you are upgrading since A9.
Yes, you're probably right I should reinstall soon in order to switch to FBE. I'll have to find a new way of backing up my data as I was using TWRP for that. I was just holding out hope that FDE support would be added back to TWRP soon.