HELP! Keep losing mobile service

[d0g]

I'm gonna lose my mind.

Last week I did a factory reset. Everything was great for a few days. Then as of Monday, my phone no longer connected to mobile network. (I'm on Visible, which is a Verizon MVNO.)

I tried the same SIM card in another phone, and it worked — but a different SIM card did not work in my phone. So it must be the phone, right?

I looked at About phone > SIM card status:

• Network: Visible
• Mobile network state: Disconnected
• Service state: In service
• IMS reg status: Registered
• Signal strength: -113 dbm

Network Cell Info Lite app showed the nearest tower and:

• SIM state: Ready
• Service state: In-Service

I tried resetting network settings and restarting in safe mode, but that didn't help. Visible said to take the phone in to Samsung repair center.

So I did that. They ran a diagnostic, and said everything was fine. They said try factory reset again.
So I factory reset the phone, again, from recovery mode, wiping with cache several times.
After, service was working. Yay!

But then a few hours later, the battery died, and ipon powering back up, I AGAIN no longer have cell service!
Could it be related to adding a work profile? Enabling dev mode?
Any bloody idea what is happening??

I'm loathe to do another factory reset, as it takes me half a day to set up everything again (Work profile authentication, etc.)

Please help save my sanity.

Thanks!