I have the retraction set to 3mm. Should it be more? What's strange is that I can use manual control to retract a few mm and it still keeps oozing.

I will try with the bed closer to the head. Simple to try.

I was wondering if my temp might be too high? Maybe the PLA is liquifying in the barrel - although once I retract I'd think that there wouldn't be pressure to cause the liquid PLA to keep coming out. But if I leave the hot-end heater running after printing and after retracting a few mm, it will continue to ooze for a couple of minutes! Not quickly as if under pressure, but a strand (nozzle diameter) that will get a few inches long.

Thanks.