This is a regression introduced in R1 2020. To reproduce it, set a menu button within a splitButton as initially hidden. Then show it with the ToolBar's
show API method.
"btn2" is shown as expected, but a js exception is thrown:
kendo.all.js:91805 Uncaught TypeError: Cannot read property 'refresh' of undefined
No js exceptions
See the following dojo: https://dojo.telerik.com/UtoTOcUD