reset an spi connection? pb with max7219

Hello, i'm working with a cheap chinese 8x8 led matrix mounted with a Max7219.
sometime ( i'm enable to determine when or why, can't reproduce bug). the display go weird... it show only one line or 2 lines of pix... after a time it come back good.
if i unplug/replug the board (a pico) everything restart well.
in first i was thinking about a prob with the graphic buffer but when i ask to show content it look full of datas...
therfore i was thinking a prob with the display...

is it possible to reduce the spi baudrate and in wich value?
or to reset an spi connection?
do i need to find an other matrix with better chip... an idea?

ps: i'm testing with low data transfer to display and it seem to work well (show on display one time on 10)
i'have a second timer with a led pulse...

regards

require("Font4x6").add(Graphics);
// spi mosi=DIN, sck=CLOCK
SPI2.setup({mosi:B15, sck:B13});
// crée le buffer graphique 8x8 en 1 bit
var g = Graphics.createArrayBuffer(8,8,1);
// connecte en spi
var disp = require("MAX7219").connect(SPI2, B14);

var texte = "Morbi leo risus, porta ac consectetur ac, vestibulum at eros. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.";

var phrase = texte.substr(0,12);
var sDerCar = phrase.substr(10,2);
var cPhrase = 0;
var compteur = 8;
var longT = 0;
var lengthT = texte.length;
var longP = 0;
var decalage = 0;
var debut = false;
var val=0;
var step = 5;

function sendData() {
  // raccorde le bout de ligne suivant
  if (compteur < -longP+decalage+1){
    if (debut) {compteur = 8; debut=false;console.log("debut");} else {compteur = 0;}
    cPhrase++;
    // si au bout du texte
    phrase= texte.substr(cPhrase*10,12);
    sDerCar = phrase.substr(10,2);
    decalage = g.stringWidth(sDerCar);
    console.log("decalage:",decalage);
    if (decalage === 0) {
      // on est en fin de texte, à la prochaine boucle, on reprend le texte au début
      cPhrase=-1;
      debut = true;
      console.log("redemarrage texte");
    }
  }

  // reset le buffer, ajoute la font, ecrit la chaine de caractères
  g = Graphics.createArrayBuffer(8,8,1);
  g.setFont4x6();
  /* une fois font utilisée, on connait la longueur de la chaine*/
  longP = g.stringWidth(phrase);
  // calcul le decalage (en pix) entre chaque bout de phrase
  decalage = g.stringWidth(sDerCar);
  g.drawString(phrase,compteur,0);
  // envoie à la matrice
  disp.intensity(0.2);
  disp.raw(g.buffer);
  compteur--;
}

function led() {
  /* var val= Math.random();
    if (val<.5) {val = 0;}*/
  //console.log(val);
  calc = Math.sin(val/100);
  analogWrite(A5, Math.abs(calc),{freq:300});
  val+=step;
  if (val>314) {val = 0; step=(Math.random()*8)+1;}
}
function onInit() {
  console.log("init programme - éric choisy ©2018");
  setInterval(sendData, 60);
  setInterval(led, 10);
  }