Greetings again, Reika!
Thank you for your patience with the wait for a response to your report. Unfortunately, it seems that the development team needs more specific information to continue to investigate this matter. It would be very helpful if you could provide a step-by-step account of how you went about testing the sweet spot for mining. Please try to include as much information as you can, especially in regards to what equipment you had on at the time. After you submit this information, we will make sure that the development team receives it, and they will try their best to re-enact what you have done. Thanks again for your patience!