My oil filter housing has been leaking as well. I've installed Advan oil cooler with stock thermostat delete and there was oil leaking between the new backing plate and the oil filter housing itself. Wasn't too bad until one day the backing plate gave way because one of the bolts that secures it to the housing was stripped inside. Pulled over immediately and topped up with oil until I was able to seal it off securely. Also checked my coolant and found a lot of oil in there as well. Seems like the seal has 'eroded' between the block and the housing and the new backing plate and the housing. Going to replace the entire housing so the bolt screws in and I've got fresh seals as well. Labour will be expensive though.
Current: Mercedes CLA45 AMG, Porsche Macan S
Past: BMW 135i, BMW E46, Ninja 300 ABS