18F1320 not capturing falling edge

    ccp1con = 0b00000101;   //capture rising edge
    t1con = 0b00010001;     //Timer1 enable, pre=2
    t3con.T3CCP1 = 0;       //Timer1 is clock source for CCP
    rcon.IPEN = 0;          //disable priority interrupts
    pie1.CCP1IE = 1;        //enable ccp1 interrupt
    intcon.PEIE = 1;        //enable peripheral interrupts
    intcon.GIE = 1;         //enable global interrupts
...
...
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void interrupt(void)
{
    if(porta.RB3){                      //rising edge detected
        start = ccpr1l;                 //store start value
        start |= ccpr1h << 8;
        ccp1con = 0b00000100;           //set to capture falling edge
    }
    else{                               //falling edge detected
        end = ccpr1l;                   //store end value
        end |= ccpr1h << 8;
        ccp1con = 0b00000101;           //set to capture rising edge
        flag = 1;
        if(end < start)
            pwin = (0xffff - start) + end;
        else
            pwin = end - start;
    }
    pir1.CCP1IF = 0;                    //clear interrupt flag
}