low memory issues with a multicock variant

I am attempting to build my ultimate multiclock style watch which is a combination of 3 of my clocks, namely "stepo", "waypointer" and "walkers clock". Each uses an arrayBuffer for the display so I need to be careful not to have any memory leaks or bad code.

Each watch face will have an init() function to create any resources and a freeResource() function to set all the variables to undefined.

(() => {
  function getFace(){
    var buf1;
    // desclare variables

    function init() {
      buf1 = Graphics.createArrayBuffer(160,160,1, {msb:true});
      // etc
    }

    function freeResources() {
      buf1 = undefined;
      // etc
    }

    // other functions as required
    return {init:init, freeResources:freeResources, startTimer:startTimer, stopTimer:stopTimer,
            onButtonShort:onButtonShort, onButtonLong:onButtonLong};
  }
  return getFace;
})();

When switching watch faces...

function stopdraw() {
  face.stopTimer();
  face.freeResources();
}

function startdraw() {
  Bangle.drawWidgets();
  face.init();
  face.startTimer();
}

function setButtons(){

  function nextFace(){
    iface += 1
    iface = iface % FACES.length;
    stopdraw();
    face = FACES[iface]();
    g.clear();
    g.reset();
    startdraw();
  }

Everything works fine for the first cycle through the watch faces. But within a few minutes I get a RED MEMORY_LOW warning at the bottom of the watch face. All the individual Apps work without memory problems.

Anyone any suggestions on if the approach should work and whre to look for memory leaks.

Hugh