Have you seen this thread?
When a player leader organizes several full raids to all congregate on one layer, that layer may hit a threshold and start trying to not add more people to that layer. For a time it will continue to allow more people to join to not break up groups, but there is a point when it reaches its absolute maximum and on the next evaluation the manager will forcibly move people off of the layer to balance the load and prevent a crash or other severe performance drops. This means that even players that were grouped and would normally be protected from being moved because they are grouped may also be moved as an emergency measure. This has been one cause for players unceremoniously being booted to a different layer; the layer simply got too full and stopped caring whether you were grouped or in combat or not.
It does as it is relevant to your issue at hand. Even the precise part was quoted for you why this is occuring. If you have better suggestions you may also fill it through the ingame suggestion box.
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