javascript issue with Mozilla firefox when zoom is above 130%

Question

We use a 3rd part framework called AribaWeb where the UI HTML is rendered by backend server, but javascript is used to handle all the UI events on the client side.

Since I am unfamiliar with javascript, i am seeking help here.

The issue we are seeing happens only with following conditions:

1. Mozilla Firefox is the browser. Latest version included. Not reproducible in any other browsers.
2. Zoom level set is above 130%
3. Fairly long form hence there is vertical scrolling

Steps and issue:

1. when users go to the end of the form and select a button or select a radio button, the page "jumps", in other words the focus shifts to the top of the page.
2. This happens very inconsistently.

I found the following old stackoverflow article and tried the solution, but no luck. jQuery Focus fails on firefox

Any hints/clues will be helpful.

I have been debugging the following function to find out clues, but unfortunately the scroll to the top of the page happens much before this function is invoked:

/////////////////////////////////////////
//   Precendence:                      //
//   first text in focus region        //
//   current browser active element    //
//   first text on page if allowed     //
/////////////////////////////////////////
focusOnActiveElement : function () {
    if (AWFocusRegionId) {
        var focusRegion = Dom.getElementById(AWFocusRegionId);
        AWFocusRegionId = null;
        if (focusRegion) {
            var firstRegionText = this.findFirstText(focusRegion);
            if (firstRegionText) {
                AWActiveElementId = firstRegionText.id;
            }
        }
    }
    if (AWActiveElementId) {
        try {
            var activeElement = Dom.getElementById(AWActiveElementId);
            if (Dom.elementInDom(activeElement) &&
                !this.modallyDisabled(activeElement)) {
                Debug.log("Focusing on element id: " + AWActiveElementId);
                var activeElementId = AWActiveElementId;
                function checkFocus () {
                    try {
                        // no active element, refocus
                        if (!Dom.getActiveElementId()) {
                            Debug.log("Refocusing on element id: " + activeElementId);
                            if (activeElement.focus) {
                                activeElement.focus();
                                activeElement.focus();
                                if (activeElement.select) {
                                    activeElement.select();
                                }
                            }
                        }
                    }
                    catch (fe) {
                        Debug.log("Exceotion ",fe);
                    }
                }

                function fcs() {
                    if (activeElement.focus) {
                        activeElement.focus();
                        activeElement.focus();
                        if (activeElement.select) {
                            activeElement.select();
                        }
                    }
                }
                setTimeout(checkFocus, 1000);
                setTimeout(fcs,0);
            }
        }
        catch (e) {
            Debug.log("Focusing exception: " + e);                    
        }
        finally {
            AWActiveElementId = null;
        }
    }
    if (!Dom.getActiveElementId() && AWAllowSelectFirstText) {
        AWAllowSelectFirstText = false;
        Debug.log("Focusing on first text: ");
        this.selectFirstText();
    }
}