Hi guys,
there is a bug in textfield's onFocus method, in code handling selectOnFocus. On IE, text selection is performed with small delay. The code fails to check, whether the textfield still has focus after the small delay.

Code:
    onFocus: function(e) {


...


        // This handler may be called when the focus has already shifted to another element;
        // calling inputEl.select() will forcibly focus again it which in turn might set up
        // a nasty circular race condition if focusEl !== inputEl.
        if (me.selectOnFocus && document.activeElement === inputEl) {
            value = inputEl.value;
            len = value.length;


            // We need a minimal delay here due to a bug that will deselect
            // the text on mouseup + focus.
            // https://code.google.com/p/chromium/issues/detail?id=4505
            // Note: This was fixed years ago but still persists in Safari, IE and Edge.
            Ext.asap(me.selectText, me, [0, len]);
        }
    },
Workaround:

Code:
Ext.define('wp.bugfix.FixSelectOnFocus', {
    override: 'Ext.form.field.Text',


    onFocus: function(e) {
        var me = this,
            inputEl = me.inputEl.dom,
            inputMask = me.getInputMask(),
            value, len;
 
        Ext.form.field.Text.superclass.onFocus.apply(this, arguments)
        // me.callParent([e]);
 
        if (me.emptyText) {
            me.autoSize();
        }
 
        if (inputMask) {
            inputMask.onFocus(me, inputEl.value);
        }
 
        me.addCls(me.fieldFocusCls);
        me.triggerWrap.addCls(me.triggerWrapFocusCls);
        me.inputWrap.addCls(me.inputWrapFocusCls);
        me.invokeTriggers('onFieldFocus', [e]);
 
        // This handler may be called when the focus has already shifted to another element;
        // calling inputEl.select() will forcibly focus again it which in turn might set up
        // a nasty circular race condition if focusEl !== inputEl.
        if (me.selectOnFocus && document.activeElement === inputEl) {
            value = inputEl.value;
            len = value.length;
 
            // We need a minimal delay here due to a bug that will deselect
            // the text on mouseup + focus.
            // https://code.google.com/p/chromium/issues/detail?id=4505
            // Note: This was fixed years ago but still persists in Safari, IE and Edge.
            Ext.asap(function(){
                if (me.selectOnFocus && document.activeElement === inputEl) {
                	me.selectTextOnFocus();
                }
            }, me, [0, len]);
        }
    },


	selectTextOnFocus: function(start, end, direction) {
	    var me = this;
	    Ext.defer(function() {
	        if (document.activeElement == me.inputEl.dom && !me.destroyed && me.inputEl.isVisible(true)) {
	        	console.log('selectTextOnFocus ' + me.id);
	            me.inputEl.selectText(start, end, direction);
	        }
	    }, Ext.isIE ? 10 : 0);
	
	    return me;
	}
    
});