Unable to commit a group that was already committed but cancelled in its execution

[dgageot]

Let's say you have a group of 1 instance. You commit the group with a change that ups the number of instances to 100. Quickly after that, you commit the same group a second time.

The result is that the update from 1 to 100 is cancelled. And the second commit is considered to be a noop.

Is that expected? cc @chungers