HI @popa, I am not really sure I understand your problem there. I have the same settings (Song settings are Sync Tracks: Start&length, Quantize to Measure: Off) yet when I change of part, it occurs as expected at the end of the loop.
Did you check the global setting named “change song part/stop song” and is it set to “End Of Loop” ?
It is easy to miss, I already mentioned in a dedicated topic that I find the configuration split between song level and global level both irrelevant for some of the flags and globally not flexible enough.
Let’s say half happy (a bit more actually but see what I say in my conclusion and the previous post from @kingofthejaffacakes . Basically we talk about an alpha, and its purpose is exactly to discuss those kind of points), but it’s already a huge move towards the right direction. Well done to the dev team… I don’t use (yet) any external device with my Aeros.