ExileApi, DevTree Offsets

[Queuete]

Hello Community,

I am playing around with the exile api plugin creation. I have experience in software developement, but my knowledge about reverse engineering is only superficial.

Currently I am trying to create a plugin which automatically sells when I am in town and got items for a chaos recipe ready.
Sadly I have some problems with opening the npc trade window.

I took a look in the DevTree Plugin and found the NpcDialog under "Only visible InGameUI".
The Parent element has an offset value FFFF... which seems to be an error value. Btw. what leads to those errors?
When browsing through its children I found an elemnt with an valid offset (408).

After that I added the Offset to the class IngameUElementsOffsets and used it in the class IngameUIElements

	[FieldOffset(0x408)] public long NpcDialog;

        public Element NpcDialog => GetObject<Element>(IngameUIElementsStruct.NpcDialog);

When I look into DevTree after that I see the Property in the IngameUI list, but when hovering its obvious its a different poeObject.
The yellow box outline is a different one, compared to the one I found in "Only visible InGameUI".

When comparing the addresses of both objects they are obviously different.

So I assume the base address is not the same as for the other UI objects?
Or have I done some mistakes elsewhere? Is there an easy way to find the base address?

Best Regards,
Queue