On the audiobus forum we researched the sync behavior of AUv3 midi generator plugins, please have a look at the thread
We found out that the root cause is a missing sample-offset in the AUv3 midi message send to the host. (That playbeat 3 doesn‘t use the host‘s midi connection is a different bug report) .
In the thread you find i depth description on how to check for that error (i offered an AUM and AudioBus session) and Corne Driesprong (dev of polybeat and cycle) offered a link to a git containg the source for correct midi sessaging including the sample-offset.
We messages your AudioModern moniker several times on that thread, but you didn‘t react - that‘s why i repost the problem over here on your own forum.