Here are some tips to avoid this:
Do not add your widgets to master page.
Instead add the widget on every page you need it. Master page elements seems to stay in background when showing in your secondary pages.
Use Adobe Muse layers.
When designing your muse page, make widgets appear in your first layer, put rest of the content in different ones.
Use “Bring to Front and Send to Back”.
Right click your Adobe Muse elements and send back desired items (sometimes it requires pressing it a lot of times) and/or send to front widgets.