The AudioPluginHost (5.4.7) does not utilize any sample offsets in MIDI Data generated by plugins, such as arpeggiators, because it uses sendBlockOfMessagesNow() instead of sendBlockOfMessages().
Can the JUCE team please take a look at this?
All of the details are in this old post that I woke back up today, but I wasn’t sure how to bring the attention of the JUCE team to the old post, so apologies if this is too redundant.
Thanks for reporting! We’ve added this in 68e0e0e.