If it's anything like the dry sump system in my Caterham CSR, if the tank is overfilled, it will spit out any excess through the vent. This could be quite a lot, up to a cup full of oil at least, so Steve's suggestion is very practical, just run the pipe to a catch tank and empty that regularly, whilst keeping an eye on the oil level. If this is the cause, the amount of excess oil should diminish to nothing after a while, and if you check where you oil level is, then maintain it at that same level.
