I am having a problem with two resources in a larger model. At the start the engineer has a maximum of 5 available resources, and the manager has a maximum of 1. As the model progresses, the engineers will go to zero, and eventually in week 8 a red zero appears. I am not sure what a red zero means, however after this point the engineers will become confused and never leave the task they are currently in, even though the task says there are no resources there.
Then in week 27 something else weird happens where an additional manager is added, so then there are 2. This will then drive this resource utilization percentage to a negative amount.
I have checked to make sure none of the tasks allow a resource to leave as a different type. And the resources should always be released upon work completion.