My Nissan Micra 1.2S 2003 model airbag light keeps flashing?

My Nissan Micra 1.2S 2003 model airbag light keeps flashing. Took it to garage who ran diagnostic and reset it. Few days later flashing again. Took it to the garage again who ran diagnostic and it showed a passenger airbag fault. They removed the dash, had a look, fiddled with the module and reset. All ok for a day, then flashing again. Garage say to replace module. Another garage say it is the wiring under the seat and when I shift the seat back and forth to access the rear seat for my daughter I am tugging on them. Which is it. How to fix it properly this time.