Google Tag Manager iframe tag string rendered on the top of the page

[Bot]

At times, the browser on a tablet displays this text on the top of the homepage -

<iframe src="https://www.googletagmanager.com/ns.html?id=GTM-<ID>" height="0" width="0" style="display:none;visibility:hidden"></iframe>

Refreshing the page makes it disappear (but reappears sometime on later page loads).

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