Map navigation tree does not stay open after refresh

1. Create navigation tree widget;
2. Add maps one after another creating a tree:

• A
  • B
    • C

1. save widget;
2. expand the added maps by clicking the small arrow [v];
3. wait for refresh, manually refresh or edit and save dashboard to force refresh.

Result:
whole navigation tree is collapsed.

Expected:
elements that were expanded, should remain expanded and not close after refresh.