Job Production Detail Report maxing out App Servers

I'm revisiting a problem we've had since upgrading from 4.4 -> 8. Our App Servers will Max out 3-4 times each week. Luckily, I've created a program that automatically resets the app servers and database.

I have configured 25 app servers on our Windows 2008 Server. This seems sufficient for most setups, but we still cannot isolate what is causing this problem. Recently, I found that in the AM a user runs a PDR for jobs, which might be the cause in the AM, but not sure when later in the after noon.

Is it normal to have app servers max out occasionally? If the PDR is causing the app servers to max out, wouldn't rescheduling during an idle time also cause the system to max out? We have sent, seriously, 20+ hours troubleshooting this with Epicor techs, with no success.