Rather than re-explaining here is a quote from another post.

"When an element is hosted to a wall within the same project file, it becomes 'not associated' any time that a change occurs that moves the wall's face away from the element: either the wall is resized down or to the side, or the wall is deleted"

"When an element is hosted to a wall from a linked project, it becomes 'orphaned' if the wall is deleted; however, if the wall is still present, but is resized so that the element is no longer in contact with the wall, it is neither orphaned nor disassociated: it just floats out there in mid-air"

To avoid... educate the Architect or use face based. I know, easier said than done when you've already sent 2 years creating the ceiling based library.

I NEVER use wall/ceiling based families because of this exact reason. When you have to deal with this there is no benefit.

well, all my stuff are face based, in fact, to my best knowledge, someone in AUGI raised exact same issue before, to my understanding it's Revit issue or i may miss something:

suppose you have quite a lot lighting fixtures or other face based stuff which are hosted on same single ceiling, suppose they're orphaned, or you simply want to rehost to another ceiling, you multi-select all lighting fixtures and rehost to same or another ceiling, now, sometimes it will work, sometimes it won't work especially when selection number is big (> 10 perhaps) which means some of them will be 'not associated', don't know why and how to avoid it?

edit: uploading RVTs for rehost test

I thought you were using ceiling hosted families because you mentioned it in your first post. Anyway your right. Even if they are face based and the original ceiling GUID is removed, than so is the link. I just tested it in 2012 with your files. I opened the Arch model deleted the ceiling and remodeled a ceiling. Upon open I recieved and error that 5 of the 8 were orphaned. I rehosted. I opened the arch model again, changed the elevation of the ceiling and size and added another portion of ceiling higher above the other. Upon open I recieved an error that "1 Instance origin does not lie on host face". So I got unexplained results. Why did it work the second time other than 1 light was slightly off the ceiling and on the first attempt only 5 were orphaned. Still appears glitchy to me. I think the best solution with this is to educate the Architects as best you can. Good luck.

I am an architect who wants to be educated. How can we help prevent this sort of thing? Okay - besides the obvious of never ever moving walls, floors, or ceilings after we've shared our model. Is it about being more aware and avoiding the unnecessary "tweeking?" There are always going to be adjustment as we coordinate systems (eg. ducts and floor joists.) What is the best way for us to make necessary changes? Should we be following rules like - don't delete ceilings; modify existing? What else should we know?

don't delete...modify...ALWAYS. Unless avoidable.

Please create your phases before the consultants begin modeling.

Create as many sub-disciplines when modeling MEP elements, so we can turn off individual elements within categories.

Place your rooms on the corresponding reference levels, not interstitial levels.

DO NOT create custom room name/number parameter tags.

(Optional, but really really needed) Create MEP friendly views that we can force as linked s (Roof plan and detail lines for crickets and drains).

Avoid masking regions in your families if at all possible (roof drains).

Please save you're RVT file in a Drafting view.

Please detach from central before uploading.

Please limit model updates to less then 12 times per day

Don't put lights in your ceilings. The void the arch light puts in the ceiling will not allow for MEP to place face hosted fixtures.

Provide ceilings even if generic. DO NOT delete ceilings, change the type or modify as needed.

Provide scope boxes for MEP to copy for areas of the building.

DO NOT delete walls/floors/ceilings. MODIFY when ever possible so MEP will not have to re-host all elements.

Provide Title Block as a seperate family fie for MEP to load.

Design options don't work at all with MEP systems.

Plan regions do not work well in MEP.(This is where we might have to force one of your links)

Keep in mind i'm not complaining. I'm just trying to effectively "suggest" what some don't know.

Please save you're RVT file in a Drafting view.
Why?

DO NOT create custom room name/number parameter tags.
Again, why?

Please detach from central before uploading.
Wahahaha, that does happen a LOT (also here on the forum btw)

Please limit model updates to less then 12 times per day
Can't always be avoided when you are working simultaniously with other parties (although I do believe the basics of a model have to be in place before MEP can start)

Provide ceilings even if generic. DO NOT delete ceilings, change the type or modify as needed.
Yeah, but they have to be defined at some point right? Here's what I would propose:
- Use Basic Ceiling for MEP to host stuff on. Since this has no thickness I can
- Use Compound Ceiling to model ceilings.
Are there any backdrafts on this...?

This used to be a huge issue in 2009, so I did a new test in 2012.
If I open a project that has one view open and is 3d shaded hidden it will take more than twice as long to open, compared to a drafting view.
45 sec for 3D, 15 sec with drafting view. I'll take those 30 seconds. Most of my time spend using Revit is waiting for it to stop thinking.
I know, how many times do we open new projects.. but saving any amount of time can surely help.

Our space tag cannot see and translate any other parameter other than Room name/Room number. We will than have to manually add them one by one name it, number it next one. This has happened on only 1 of my projects, but it was a nightmare keeping up with room changes. If we use it the way it is intended everyone benefits.

Nope. As long as it's in there and gets modified from there on out it's good.

If you imagine your working in an AEC firm. You go to delete a ceiling and Revit tells you at that moment 16 lights will be orphaned/unhosted or deleted, You would probably reconsider. These are the message we get and it creates extra work.

BIM is just a tool to do what we have done for thousands of years. If we all communicate more and use this software how it is intended we will all be better off.

Thanks for asking why.

Don't worry - I know you're not complaining. This is exactly what I asked for! Thanks very much.

Thanks for the explanation. Hope this helps in my next integrated design project...