Corolla CE 98 - Seat Belt sensor/buzzer problem

I have a Corolla CE 98.

1. The car seat belt sensor buzzer is not working.

1. The car seat belt sensor light is not proper. Sometimes it won't function at all. It won't blink when the key is turned to ready position, it won't blink if driver seat belt is not on.

2. Most weird is that sometimes when the driver's seat belt is buckled properly, the light will start blinking and will stop when the belt is removed from lower buckle. However the buzzer remains dead even the light is blinking incorrectly

Can anyone help me with this? I don't want to go to the expensive dealership if its something i can fix myself.

Look forward to your help and tips

P.S. I recently had some problems with the car's exhaust system and got convertor joint replaced with flex pipe as diagonsed by Meineke last week. The problem started after this but they say exhaust work is not related to sensor at all

Thanks,