Why do nameplates behave strangely in combat?
Nameplates are ultimately "owned" by the WoW Client. Aloft just takes control of them when they become visible, and "customizes" them.

The problem is, Blizzard does not allow "nameplates" to be changed in combat. This restriction does not apply to the visible parts of nameplates (status bars, text, etc), but it does apply to the "parent" object of every nameplate (the "parent" nameplate frame), which is what the WoW client uses for basic placement, visibility, and mouse sensitivity of all nameplates. The visible parts of the nameplate (the health bar, text, etc) can be modified during combat, but not the basic characteristics that are controlled by the "parent" nameplate frame.

So, in combat, you cannot:
  • Change the height/width of the "parent" nameplate frame (this is how packing height/width are implemented, which in turn affects basic placement of the visible parts of nameplates). This affects Aloft "Frame" options.
  • Hide individual nameplates (via the "parent" nameplate frame), or make them visible. This affects Aloft "Visibility" options (and can be worked around by enabling the AloftAlpha module and using "alpha" to control visibility, enabled via Aloft's "Visibility" options).
  • Turn the mouse on or off (which must be controlled via the "parent" nameplate frame). This affects mouse sensitivity (controlled by Aloft's "Frame>Enable Mouse" option).

(Note: As of WoW 3.3.X, the player's current target nameplate is not sensitive to the mouse in any way, not to mouseover and not to right-click. Clicking through the nameplate onto the associated unit 3D model is possible. This is also discussed in this FAQ.)

The other thing that happens is that the WoW Client "recycles" nameplates. When a unit goes out of range and its nameplate drops (disabling nameplates has the same effect), the WoW Client doesn't delete the nameplate, it "detaches" it from the unit and sticks it in a pool. When a new unit (the same, or a different one), comes back into range and its nameplate becomes visible (enabling nameplates has the same effect), it pulls one of these nameplates out of the pool at random and "attaches" it to the unit (and updates unit name, level, health, etc, and makes it visible, in the process).

when Aloft takes control of these nameplates, it sets them up (extensively customizes the placement, appearance, visibility, mouse sensitivity, per the user's preferences). This configuration remains when the nameplate is "recycled". As you play the game, Aloft will eventually gain access to all the nameplates in the pool as they are assigned to units and made visible, and will configure them all. Occasionally the pool will be empty, and a new nameplate will be created by the WoW Client.

So, in combat, if you are lucky, when a new nameplate appears it will be a recycled one that Aloft has already configured, and it will still have the Aloft setup from the last time it was used (including placement, size, and mouse sensitivity). If you are not lucky, the WoW Client will create a new nameplate, or use one from the pool that Aloft has not already configured, and it will retain some "default" settings from Blizzard. Aloft will not be able to change those "default" settings until you leave combat.

As well, it is possible that nameplates that are not used for a while are eventually deleted from the pool (i.e. the pool shrinks). When that happens, there will be one less Aloft-configured nameplate available for re-use, and the likelyhood that the WoW Client will have to create a new un-configured nameplate in crowded sitiuations increases.