If you're having problems with your Vault-Tec lights in-game, you can get them fixed by downloading the mod that was created by fadingsignal and uploaded to the official Bethesda' site. It fixes all of the lights in the game, except for the utility light, which is above your head and doesn't change in intensity. If you want to use it with another mod for a more realistic effect, you can use the one that was created by fadingsignal and uploaded to the official Bethesda' site.

You can either download it through NMM or extract it to your directory.