Certified GKH Gardening Expert
I am not sure what mim oil is, but if you have not tried neem oil, I would recommend it, though you may need a few applications. If you have tried that, I would try insecticidal soap.
When you use these things to treat the scale, wash the plant first to get off as many of the scale as you can. After you treat the plant, continue to treat it weekly for a month or two. What is likely happening is that some scale are in the soil and they do not get treated when you treat the plant and then re-infest the plant once the others have died.