So I ended up finding a Mr. Gutsy model during my exploration of one of the vaults. Cool, I thought. It would look pretty sweet on display. I took it to my house in Diamond City and place it on a shelf with some other artifacts I've come across. But after a fast travel back I take a look at the shelf and notice it's gone. The other items are there but not the Mr. Gutsy model. Looked all over the floor to see if it had gotten knocked off, but then the other items would surely have moved too. I couldn't find it. Anyone else have this problem?

I'm hearing some items are kinda janky like that.

Now, if you go into build mode, can you manually move that type of item? I feel that might help with that.

I've been carrying that & other types with me, forgetting to put them on display. I was gonna place them in my Diamond City pad but you've put me off from doing that. But I haven't noticed anything from there disappearing... yet. I've done it up quite nicely & seems to be a stable place to decorate. Maybe I should do a test run with a save I can go back too if all fails.

"Item jumping" is what I call it.
It's when you take the time to set up a nice little display and as soon as you leave the area and come back, or an NPC farts in Australia, all the items you just spent three hours carefully placing just jump onto the floor.

It also happens in F-4 with the magazine rack.
I have to keep my magazines in a filing cabinet.

I found that when I use the turn table magazine rack (the one shown on the F4 start menu) they all fell on the floor when I returned to my home. So I used the wooden display rack for my magazines instead which works much better, plus its a better display stand for your magazines. Try experimenting with the other racks in the options menu. I now have four wooden display stands as I'm finding so many magazines, which is cool.

The turn-style magazine rack works for me.

BUT....my items do fall to the floor through whatever object it is placed on.....

About the magazines rack, I've had the issue with it dropping mags sometimes. But they're still considered stored apparently, so you don't need to pick them up. Just open the transfer screen on the rack, and everything will be back in place when you exit.