Replacement of oil seal of pedal 125 motorcycle gearbox due to oil leakage. Why is it still leaking? thank you

If it is confirmed that the replaced oil seal leaks oil, you can check whether the oil seal is improperly installed, or whether the oil seal is of poor quality, and whether there are problems with the engine case and shaft where the oil seal is installed, such as unsmooth and uneven surface. , and check whether there is too much oil in the engine and whether the breather pipe on the engine cylinder head is blocked or not well ventilated.