This is a known problem. You can check KM00465514, which says

> In QTP 11, both Browser().Sync and Browser().Page().Sync statements
correctly use the Browser Navigation Timeout (default to 60 secs) to wait
for pages to load. Customer relies upon this timeout to synchronise slow
operations in their application.

>In UFT 11.51, Browser.Sync has the same behaviour as in QTP 11 (uses the
Browser Navigation Timeout as timeout value for the Sync method). However,
Browser().Page().Sync uses the Object Synchronisation Timeout instead as
timeout value.
>Workaround: Replacing Browser().Page().Sync by Browser().Sync

So, try changing to just .sync on the Browser object instead of the Page object.