Here is a REPL test page. If the user navigates forwards and backwards via the Wizard buttons, the TreeView checkboxes persist their state. If the user navigates via the Stepper, the checkbox state is not retained.

The issue is triggered by the TabStrip.

A possible workaround is to prevent Stepper clicks with CSS:

.k-tabstrip .k-wizard .k-stepper .k-step {
  pointer-events: none;
}