Hi there,
Found an odd behavior in the Conflict resolution popup. It doesn't seem it's constant because I can't reproduce it in your Conflicts demo https://bryntum.com/products/gantt/examples/conflicts/.
When you click on cancel the first time, the popup closes and opens again so you have to cancel 2x.
If you then try to make and adjustment that violates the same constraint and the conflict resolution popup opens again and you click on cancel again then your changes are not reverted (cell stays in edit mode).
Here is a video on how to reproduce the issue in your Advanced demo https://www.loom.com/share/5394dce1364843f5b9558d9437663adf?sid=41cbd798-bda6-467a-9d83-f4967c7f9d1f.