If on Resource screen cell's borders are not straight relative to others (as on screenshot below), please try to:

  • reset scaling in your browser;
  • change screen resolution;
  • try to change scale of UI elements in your OS.

This is a problem with DHTMLX library: for some browser window scales and screen resolutions grid doesn't render correctly

Above problem appears in few posts on DHTMLX forum:

and on their tutorial examples