One of the known ‘quirks’ of the cymatics is indeed that all tracks must have identical lengths.
that already started with LP, and I believe the issue still continues.
There are other threads describing early stopping of multitrack songs and other similar issues. These i remember even from the early days with LP16. Once I understood that according to the cymatic logic, all tracks need to have the same length, I made this a standard part of my workflow and it all works well. Even thru uTool.
i would hope that our cymatic friends will overcome this issue in the future, but for now with equal track lengths, it all works fine.
Hope that helps to solve your issue