Hi.
Lets say i have 10 layers in my timeline. I create a group and want to move - lets say - 5 layers into this new group. I select layer 2…6 and move these layers by dragging with my mouse into the group.
Result: only the 1st and last selected layer become moved.
(Aseprite 1.2.3, on Windows)
Hi there! Are you selecting all layers or only 2 and 6? To select 5 layers you have to press the mouse button in one of them and then drag the mouse to the last one and release the mouse button, for example:
There is a difference between this (only layer 2 and 5 will be moved):
And this (all layers will be moved inside the group):
Thank you !
I got the Idea 
It seems the bug was in front of the computer 