Hello
I don't know if this guide will fully fix your problem, but it is here to help try to fix it.
Okay if you have buildings in you repack that are wmo's and when you spawn them they turn into white and blue boxes (Usually if you download extra game objects) I will try helping you fix them.
First off what you have to do is open up your database manager you use for example Navicat is what i use.
Then open up your database for example Arcemu, then find the table called gameobject_names.
After you have done that find your objects you have added and look at there type it says they are usually people just make all of them 5 so that makes a problem.
When you have found your item change its type to 14 which makes it a map object or building.
Also if 14 doesn't work here is a list of all the types and what they do
0 - Door
1 - Button
2 - QuestGiver
3 - Chest
4 - Binder
5 - Generic
6 - Trap
7 - Chair
8 - Spell Focus
9 - Text
10 - Goober
11 - Transport // elevators, subways, railcars, etc.
12 - Area Damage
13 - Camera
14 - Map Object
15 - Mo Transport // all of the boats between areas, like Ratchet to BootyBay, have this type
16 - Duel Arbiter
17 - Fishing Node
18 - Ritual
19 - Mailbox
20 - Auction House
21 - Guard Post
22 - Spell Caster
23 - Meeting Stone
24 - Flag Stand
25 - Fishing Hole
26 - Flag Drop
If this doesn't work please post below and I will try to help you.
P.S Sorry if someone already made a guide like this, I couldn't find one so I made one.