I have been working in the Designer 2.4.2 Beta for about an hour and have had 4 hard crashes, when applying gradients or adjusting a Cog primitive that is part of 3 symbols that are synced in certain aspects, but have individual edits on them (e.g. contour and different gradients) as well. Unfortunately, I haven't yet found any reliable way to reproduce this, but it's not looking good. None of this is using any of the functionality introduced in 2.1 - 2.4.