The "CAUAJM_W_10548 Machine ****** is unavailable due to lack of resources" is a generic message This message appears to be new in 11.3.6 SP1 and is related to a job not being able to start due to lack of Autosys virtual resources for a particular job.
this mean that there is no available virtual resource units at this time.
we have test jobs that have a dependency on a renewable resource, and if we define the resource to 1 we see lots of these messages, but if we increase it to a value that is higher than the level of concurrency we are trying to push, then we don't see the message.
we did some more testing and was able to confirm that the CAUAJM_W_10548 message being generated due to running multiple test jobs at the same time requiring a quantity of 1 for a renewable resource with a total quantity of 1...