Good evening esteemed car gurus.
My car a Toyota Corolla 2010 automatic transmission model is having serious gear issues.

It started when I took it to mechanic to change gear box cop and shaft because of the noise it makes and constant vibrations. After changing all these the car started having sluggish movement, skips and de-accelerates on motion. At times when I pedal on motion it will be as if no gear was engaged until it picks. I was advised to change the gear oil, clean filter and plugs which I have done but the issue still continued. Pls car experts what could be the cause of this problem and where can I fix it in Abuja.

Thank you.