On every bootup I get the "Android is updating" (Optimizing apps) screen.
I've tried a few methods. I deleted all custom odex files in
/data/app dictionary and deleted the dalvik cache but it's still there on every boot up. How can I get rid of it?
Cache partition wont write correctly - might be damaged.
latest twrp's have fsck (disk check)
Else wise, I have no idea what ur runnin.
It might be the dalvik cache which is broken however you can try to reinstall your ROM flash the Google apps if you want to. Then wipe the dalvik cache, you might want to wipe it before reinstalling your ROM