Inexplicable error on Chrome

Hi Clifton,
I have spent hours trying to understand what's happening. I show the second page of my tbk in an iframe using pgGotoURL(). No problem with Firefox:

but in Chrome this happens:

I have tried all kinds of things including console.log(iframe.contentWindow.scrollY) but it returns 0 as it should. This only started happening this morning. Have you any suggestions, please?
John
I have spent hours trying to understand what's happening. I show the second page of my tbk in an iframe using pgGotoURL(). No problem with Firefox:

but in Chrome this happens:

I have tried all kinds of things including console.log(iframe.contentWindow.scrollY) but it returns 0 as it should. This only started happening this morning. Have you any suggestions, please?
John