Like all good EV owners I spent last friday nite under it changing the oil
and filter. I saw something that I had seen before on Vanagons:

There is an oil cooler on EV's just like the ones on Vanagons. It is held
onto its mounting by a large, flat nut. When changing the filter on vanagons
it's easy to see/feel if this nut is tight. If its not it will loosen and in
time prevent the filter/cooler from seating. Then it will be a mysterious
oil leak. Until this nut is tightened no amount of torque on the filter will
 seal it or the oil cooler seal.

On the EV's next filter change check this nut! Its hard to see but is very
important.