Soundtoys 5.3.1 will be the final patch before they add support for macOS Catalina, which will require them to drop 32-bit plug-in support for both Mac and Windows.
Little AlterBoy and PrimalTap sync fix
When using Little AlterBoy on a mono track in DAWs like Ableton and Cubase that process mono tracks in stereo, sometimes it was possible for the left and right channels to shift out of sync. This could add an unwanted "phasey" sound to the vocal, or create a slight difference in the sound of the left and right channels. This bug could also affect PrimalTap's Freeze mode. Soundtoys 5.3.1 fixes this issue in all but very rare use cases.
NOTE: This fix may change the sound of some audio tracks that use Little AlterBoy and PrimalTap (in freeze mode). If you think the out-of-sync sound is an important part of some of your tracks, SoundToys recommends that you bounce or freeze those tracks to preserve the exact sound they have today.