[Q] blinking gray triangle in notification bar

question: there's a blinking gray triangle outline in my notification bar.. why??
occasionally it will disappear, but it comes back quickly.. it also disappears if I reboot, but comes back quickly again. it wasn't there until I messed up my phone and had to restore it (see list below)
it has been like this for weeks..

I have attached a screenshot - you can see the gray triangle in the notification bar. it blinks on and off.
also, in settings->about phone->network, "Network" says "Unknown". don't see anything else unusual.

I noticed sometimes my text messages will not send, also gps seems to be worse.. not sure if either of these are related.

tried searching, found some stuff saying it's about roaming (but I'm not roaming), also found some stuff that led me to believe I might need a new sim card (can't seem to find those posts anymore though)


here's some history:

1. accidentally took KitKat OTA while rooted, couldn't boot into rom, recovery, or download mode
2. followed this guide to fix that issue
3. restored a backup (rooted stock 12B) from twrp
4. followed this guide to get back into rom
5. this is when I noticed the blinking triangle
6. tried flashing radio.. didn't do anything
7. noticed IMEI was zero, thought that might be the cause
8. used this guide, seems to have fixed IMEI but triangle is still there
9. gave up for a few weeks, now here I am!

edit: the triangle just disappeared for a few minutes. during that time, I could not send text messages or make calls, but data still worked.

a day later and nothing

another thing I noticed: on the lockscreen, it doesn't say "verizon". it's just blank.

I'm going to go completely back to stock as a last resort, but hopefully someone can help me figure this out