Keeping AdvancedRobot instance in static field

When keeping AdvancedRobot instance in static field, robot will show warning:

Static references to robots can cause unwanted behaviour with the robot using these.

However I've been using this pattern (the way robocode can't detect, and I cannot avoid as well) since the first day I write robocode. However, robocode did not mention what's wrong with this pattern. Do anyone know what's the exact meaning of this warning?

I think the risk is that the static robot reference is not guaranteed to be valid after a given round, so if you don’t update the reference things may not work as expected.

Yes, that's also what I guess, and since I'm updating the reference every round, I guess it would not be a problem. However, since robocode did not say what unwanted behavior it is, I'm worrying about more problems: race condition (since each round you have a new thread), GC problem (no longer a problem since robocode cleans static field each battle) and more

Since you're updating it every round, why do you need it to be static?

Ease of access, probably. I was doing the same before my big inversion of control refactoring.

because I’m simply making everything under a static variable, just like lazy singleton.