run the attached example:
1.
click button "Case 1" followed by "update first 2 Lvl 1"
-> children of "Node 2 L1" move to the top of the tree (open/close "Node 1 L1" fixes the problem, even after invalidate)

2.
click button "Case 2" followed by "update first 2 Lvl 1"
-> "Node 2 L1" disappears
-> Error is shown "Failed to mount: Cannot read property 'lastChild' of undefined"

2.b)
click button "Case 2"
open node "Node 2 L1"
click "update first 2 Lvl 1"
-> "Node 2 L1" disappears
-> Error is shown "Failed to mount: Cannot read property 'lastChild' of undefined"
-> children of "Node 2 L1" move to the top of the tree

the problems can also reproduced using "Update All" instead of "update first 2 Lvl 1". But to keep example simple the minimum number of updates is used to reproduec the error for easier debugging.

When fixed use "fillRandom" and "update all" to identify potential other error constellation.