Mic issue, receiver can not hear caller from time to time

hi

I sometime ago changed the power/volume flex cable for a costumer on an iPhone 5.

She yesterday returned claiming that after the repair when she calls someone, the receiver can not hear her well. They say she is falling out alot and other times her voice gets very loud and unclear.

I checked the phone through and even replaced the mic/jackstick etc, but the problem persists.

Has anyone else here experienced this ?

Please, has anyone experienced this ?

everything seems to be fine, few short interruptions during a call.