I've purchased MixBox and really like it, however there is an issue with tempo sync'd devices that limits their use unfortunately.
Any module with a sync option (e.g. Autopan, LFO Filter, Tremolo, Opto Tremolo, Uni-V, or the Slicer) do indeed sync to the host tempo, but don't appear to sync to the DAW transport. That is, if you stop playback, go to the start of a bar and start again, the syncing doesn't reset (so panning will be out of phase, or the slicer will be delayed even though in time).
I've tried both VST2 and VST3 versions, in Reason and in Studio One, and the issue is the same in each case.
Unfortunately, without syncing to the transport it means certain modules (especially the Slicer) are far less useful than they would otherwise be, as they are never in sync with the rest of the tracks in a session.
Is this something that is known and will be addressed in a future update? I notice that the same issue applies to SampleTank's syncable effects too.
