post your code and i will have a look
it works ok for me

https://youtu.be/Jxd4a4XmuDo



Code:
'****************************************************************
'*  Name    : UNTITLED.BAS                                      *
'*  Author  : richard                                           *
'*  Notice  : Copyright (c) 2022 caveat emptor                  *
'*          : All Rights Reserved                               *
'*  Date    : 11/10/2022                                        *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*          :                                                   *
'****************************************************************
#CONFIG
  CONFIG  FOSC = INTIO67
  CONFIG  PLLCFG = ON
  CONFIG  PRICLKEN = ON
  CONFIG  FCMEN = OFF
  CONFIG  IESO = OFF
  CONFIG  PWRTEN = ON
  CONFIG  BOREN = SBORDIS
  CONFIG  BORV = 190
  CONFIG  WDTEN = OFF
  CONFIG  WDTPS = 32768
  CONFIG  CCP2MX = PORTC1
  CONFIG  PBADEN = OFF
  CONFIG  CCP3MX = PORTB5
  CONFIG  T3CMX = PORTC0
  CONFIG  HFOFST = ON
  CONFIG  P2BMX = PORTB5
  CONFIG  MCLRE = EXTMCLR
  CONFIG  STVREN = ON
  CONFIG  LVP = OFF
  CONFIG  XINST = OFF
  CONFIG  DEBUG = OFF
  CONFIG  CP0 = OFF
  CONFIG  CP1 = OFF
  CONFIG  CP2 = OFF
  CONFIG  CP3 = OFF
  CONFIG  CPB = OFF
  CONFIG  CPD = OFF
  CONFIG  WRT0 = OFF
  CONFIG  WRT1 = OFF
  CONFIG  WRT2 = OFF
  CONFIG  WRT3 = OFF
  CONFIG  WRTC = OFF
  CONFIG  WRTB = OFF
  CONFIG  WRTD = OFF
  CONFIG  EBTR0 = OFF
  CONFIG  EBTR1 = OFF
  CONFIG  EBTR2 = OFF
  CONFIG  EBTR3 = OFF
  CONFIG  EBTRB = OFF
#ENDCONFIG
    




     DEFINE OSC 64
    DEFINE DEBUG_REG PORTB
    DEFINE DEBUG_BIT 7
    DEFINE DEBUG_BAUD 9600
    DEFINE DEBUG_MODE 0
    LATB.7=1


   
    #DEFINE colours 1   ;1 mono 2 rg or 3 rgb
    width  con 128      ;
    height con 64      ;
    'use serial i/f
    #define  stserial 1
    include "grx.pbpMOD" 
    include "st7920.pbpmod" 
    include "font.bas"
    include "bignum.bas"       
    include "bigchr.bas"
    BUFF       VAR BYTE[32]
    OSCCON=$70
    OSCTUNE.6=1
    while ! osccon2.7 :WEND    ;wait for pll
    ANSELB=0
    ANSELC=0
    ANSELA=0 
'      serial   spi pins used
'      e is sck        latc.3
'      rw is sdo       latc.5
'      rs is cs         latc.1
    'trisc = %11010101 ;cs,sck,sdo are output
    trisc = %11010101 ;cs,sck,sdo are output
    TRISB = %11111111
    TRISA = %11111111


              
    n var word


    gosub st7920_init    'graphic mode


    OSCCON=$70
    OSCTUNE.6=1
    while ! osccon2.7 :WEND    ;wait for pll
    
    ANSELB=0
    ANSELC=0
    ANSELA=0 
    
    Pause  500      ' LCD initialize time
    lcdout $FE,1
    gosub st7920_init    'graphic mode
    gosub grf_clr
    n=0
    SETFONT bignum
    bgcolour=0
    
 main:   
    n= n+1
    colour=1
    fillrect 39,29,46,16 ; this is a guess about your font size
    ARRAYWRITE BUFF,[dec4 n,0]
    DMDSTR 40,30, Buff,0
    colour=0
    fillrect 39,9,46,16 ; this is a guess about your font size    
    DMDSTR 40,10, Buff,1
    gosub show 
    pause 1000
    
 goto main