[Maya]loadUI in window has white/blank space

I’m having a strange issue with pm.loadUI() creating white/blank space inside the container window.
loadUIWhiteSpace

The tool is here:
https://www.highend3d.com/maya/script/rename-tool-for-maya-100434

The renameToolUI.py file contains the code for loading the .ui file:

import pymel.core as pm
import ctypes.wintypes
import sys
import importlib

CSIDL_PERSONAL = 5       # My Documents
SHGFP_TYPE_CURRENT = 1   # Get current, not default value

buf= ctypes.create_unicode_buffer(ctypes.wintypes.MAX_PATH)
ctypes.windll.shell32.SHGetFolderPathW(None, CSIDL_PERSONAL, None, SHGFP_TYPE_CURRENT, buf)
print(buf.value + '/maya/scripts/renameTool/renameTool.ui')
path = str(buf.value) + '/maya/scripts/renameTool/'
sys.path.append(path)

import renameTool
importlib.reload(renameTool)

window_id = "renameWidget"

if pm.window(window_id, exists=True):
    pm.deleteUI(window_id)

window_ui = pm.loadUI(f = path + 'renameTool.ui')
window_ui = pm.showWindow(window_ui)

Has anyone seen this before?
Thanks.