How to wait for an iframe to load completely on the page

[MarcosPereira1]

I'm testing an application that has many iframes, one of them loads several requests and I didn't find any content related to a wait that waits for my entire iframe to load completely, I tried using cy.intercept but it was quite long because it has several requests that I need to wait, I used cy.waitUntil on loading but it was also not possible to wait, the only one that had a positive result was using cy.waitForNetworkIdle, but it turned into a test that passes sometimes yes, sometimes...

I used this command:
cy.waitForNetworkIdle('+(POST|GET|HEAD)', '*', 20000)

it expects all requests correctly

after running for a while I got this error

could someone help me with this error or with another solution that can help me better