Hi,
That was my idea of what was causing this issue, it's failing to switch current browser to the one containing the page I am targetting. But I don't think this is something impossible as the documentation states:
However, in order to reduce ambiguous recognition issues, TestComplete can select the appropriate browser depending on the URL of the requested page. If the Browser object that was returned by the Sys.Browser() method does not contain the Page object with the specified URL while another running browser displays such a page, TestComplete automatically reassigns the method’s resulting value to the Browser object that corresponds to the browser displaying the page with the requested URL.
From: https://support.smartbear.com/testcomplete/docs/reference/test-objects/members/sys/browser-method-sys-object.html
If a page I am looking for is in another browser. TestComplete will return the correct browser object for me to use containing that page which I believe TestComplete has been doing for us the past few releases.