Hi,
not sure what the issue is, but it does not seem a PotentialDeadlockException from the stack trace
is deactivateInternalTenant and activity or the main workflow method?
This post Best way to create an async child workflow - #2 by maxim shows how to start workflows async if that is what you are trying to do.
What is exactly in line 90 (ScheduledTenantDeletionWorkflowImpl.java:90)?
Antonio