For reference here as well, depending on if using a site builder one of the domains/parent in the stack of iFrames might change each time you save the site. Which can make it interesting to build the parent stack. (Depending which one will detemine the solve). (But the use of localhost when testing/building OP’s site suggests that a site builder and thus an iFrame stack isn’t/shouldn’t be present, but might be testing before copy/pasting to said builder, which then invalidates the test as the test environment doesn’t match production)
Further reading on the Wix/embed mega thread - The great big "I'm using WIX/SomeWebsiteMaking Tool and I don't know how to fix my embed" thread
For optimal advice here please provide the page that is throwing the fault.