Previously running 15.1

No need for a full wipe.

Update to 16.0

Use previously installed TWRP to upgrade to

lineage-16.0-20190303-nightly-oneplus3-signed.zip
open_gapps-arm64-9.0-mini-20190304.zip

Nightly updates start failing

After a few days, nightly upgrades started to fail, with

assert failed: op3.verify_modem("2018-12-06 00:49:
24") == "1"
Updater process ended with ERROR: 7
Error installing zip file '/data/lineageos_updates/
lineageos-16.0-20190309-nightly-oneplus3-signed.zip'
Updating partition details...
...done

Updating TWRP did not help.

Details:

cp twrp-3.2.3-1-oneplus3.img twrp.img
adb reboot bootloader
fastboot flash recovery twrp.img
fastboot reboot

The problem appeared to be modem compatibility, so:

Update firmware and modem

Latest was Stable5.0.8+Firmware+Modem_OnePlus3.zip

adb push Stable5.0.8+Firmware+Modem_OnePlus3.zip /sdcard

Go into recovery and update with TWRP.

After this, nightly updates work again.