Default [Q] System errors even after a factory reset, help?

Thanks in advance for any advice given!

I was running Mahdi Rom, one build behind the latest, and all I can remember before things went tits up was I was updating a couple of apps through the play store.

Then I started getting repeated androidsystemui processs ended errors every few seconds. I rebooted into recovery and wiped everything through TWRP. Still got system errors after reboot, couldn't even get through the google account login and sync.

Downloaded the LG mobile support tool and flashed back to total stock -- can't go wrong, right?

Now I'm getting android.system.acore proccess ended errors, and Google Play won't run at all. Any hope, or am I fried?

Fingers crossed,

Yojimboj