Another reason of high content of oil in the compressed air is when the compressor is working on very low load. If you use the compressor just for a couple of minutes then the oil cannot reach the normal working temperature (68 - 86 degrees C). In such case condensate appears in the oil and the oil becomes in foam (coagulates) and the coagulated oil is passing through the separator filter in the compressed air.
Stop the compressor and wait for a couple of hours. Then check if there is foam in the separator tank and airend. If there is foam instead of oil free of bubbles that means that the oil is coagulated. If this is the scenario, then change the oil, oil filter and separator filter and start using compressor for longer time until it reaches normal working temperatures and work for at least 45 minutes.