Incorrect Resource Penalty

In my last game had a strange case where I got a resource penalty notification for oil when I had more than I was using. I'm not sure this affected the combat as it didn't show up as a -50% modifier.

The notification you mention appears often in my games when upgrading a unit that requires a resource to a unit which requires the same resource. This happens especially when I have 0 of that resource: I have used all of that resource for my existing units.

Trust the indication at the top of the screen. The notification should not appear in those situations. It should be fixed, but it only causes temporary concern for me. However, that was a great concern for me the first few times I experienced it.

Yes, I know what you mean. In this case I had upgraded my units a while back. So maybe its just the notification getting stuck. I've had this problem with ancient ruins and barb camps. Which aren't there anymore but will highlight if you click the notification which doesn't go away for a while.