L2J Server

I am wondering what problems are cause if for example you reload multisells, htmls, teleports and configs.

From experience i know that some stuff like reloading zones break after a few reloads.

The reason i ask this is because i never had any issues while reloading htmls, multisells, teleports and configs on a live server.

Its a general warning I guess, not everything is causing issues.
For example reloading skills cause issues on live servers if players are using skills when they are excactly being reloaded (many NPEs).
Also reloading scripts will end up in errors and some of them will cause double spawns.

Reloading skills will cause certain parts of code to hold old skill information, thus no update till player relog or monster die?
Reloading scripts can cause NPEs if they should be triggered when reloading.
I don't see much problems reloading HTMLs.