During the last LineageOS update, after having rebooted the phone I got a message saying “ensure your vendor image matches OMP7.18.1005.003”. After a little bit of research I fixed it easily, the reason for that to happen is that LineageOS doesn’t ship vendor, bootloader or radio as part of the update. So it has to be done manually.
The first thing is to identify the version of the image that you need, for my bullhead (Nexus 5X) I needed “OMP7.