Custom indicator doesn't show data for all bars.

[0Tom]

On my indicator that I am making data is only displayed for the most recent 50% or so (it varies) bars and then after that it does not display anymore data. Here's a picture showing what I mean https://imgur.com/a/NquoQLo .

property indicator_separate_window
#property indicator_buffers 1
#property indicator_plots   1
#property show_inputs

extern int period ;


double cnv_tb[ ] ;
double nv[ ] ;
double cnv[ ] ;
double cnv_ma[ ] ;


int OnInit()
  {
  SetIndexBuffer( 0 , cnv_ma ) ;
  return( INIT_SUCCEEDED ) ;
  }


int OnCalculate(const int rates_total ,
                const int prev_calculated ,
                const datetime &time[ ] ,
                const double &open[ ] ,
                const double &high[ ] ,
                const double &low[ ] ,
                const double &close[ ] ,
                const long &tick_volume[ ] ,
                const long &volume[ ] ,
                const int &spread[ ] )
   {
   
   int bars = rates_total ;
   
   ArrayResize( nv , bars ) ;
   ArrayResize( cnv , bars ) ;
   ArrayResize( cnv_ma , bars ) ;
   
   double close0 ;
   double close1 ;
   double volume0 ;
   nv[ bars - 1 ] = 0 ;
   for( int i = 0 ; i < bars - 1 ; i++ )
      { 
      close0 = iClose( NULL , NULL , i ) ;
      close1 = iClose( NULL , NULL , i + 1 ) ;
      volume0 = iVolume( NULL , NULL , i ) ;
      if ( close0 - close1 > 0 )
         {
         nv[ i ] = volume0 ;
         }
      else
         {
         if( close0 - close1 < 0 )
            {
            nv[ i ] = - volume0 ;
            }
         else
            {
            nv[ i ] = 0 ;
            }
         }
      }
      
   cnv[ bars - 1 ] = nv [ bars - 1 ] ;   
   for( i = bars - 2 ; i  >= 0 ; i-- )
      {
      cnv[ i ] = cnv[ i + 1 ] + nv[ i ] ;
      }
      
   for ( i = 0 ; i < bars - period + 1 ; i++ )
      {   
      for( int j = i  ; j < i + period ; j++ )
         {
         cnv_ma[ i ] += cnv[ i + j ] ;
         }
      cnv_tb[ i ] = cnv[ i ] - cnv_ma[ i ] ;
      }
       
   return( rates_total ) ;
   }