@Hojack
If you read through my thread your issue where you had the spacer missing is exactly what happened to me, except you caught it much earlier then I did, fortunately for the sake of your transfer case housing,
I made a spacer like you did that was actually heavier duty and it only lasted about a month. The transfer case input gear actually puts a load on that spacer in that direction due to the direction of the helically cut gears.
Advance Adapters has the spacers, that are supposed to be included in the kit, and you will see that they are much larger thickness, and they’re hardened.
I called them and they sold me one individually.