Using OS X 10.9.3, Alchemist V3 64-bit (3.2.20.32351 but also tried the first RC) makes Renoise (3) stall on loading projects containing it. Beachball of death and the only way out of it seems to be force quitting Renoise. I haven’t tried 32-bit V3.
Disabling AU’s in Renoise’s preferences and trying to open the same projects, they load. Resaving them having just removed Alchemist V3, then re-enabling AU’s in Renoise’s preferences, they load too. I can’t reproduce it with versions of Alchemist prior to V3. No problems adding Alchemist V3 to and using it in a project. Just when trying to load projects containing it. Made a ticket with their support too. Thanks.
EDIT: FLUX support says they have fixed it. Waiting for a bugfix release next week or so.