My mileage is not that high though, 57k only. But it might have something to do with my car hitting a speed bump kinda hard as problem started after that incident.

But thanks for confirming that this is a common issue, was afraid it was the workshop trying to pull a fast one on me. I guess I'll go back to the same service center again for them to further check and see what's the problem. Or do you think it's better to straight send to the place you did rm4k belt replacement (Summer Auto Transmission) for them to check there?