Hi, awesome mod. I have owned this game since it was in alpha and I am always in awe of modders keeping their stuff up to date, respect to you.
Couldn't find this as an open issue on GitHub. KSP 1.12.3.3173
When your mod overwrites an old default illuminator already on a vessel the 'lit' version does not show. it can be switched on/off and tilt fine, it just does not 'glow' when it is on.
Hope that makes sense?
Keep it up!