Opening multiple custom OAF pages simultaneously

We have custom-developed OAF pages which we open up from Oracle Apps responsibility.  The custom pages are working OK while we only have 1 open page at a time.  But when there is more than 1 page open simultaneously, we encounter different errors like "stale data" or "primary key could not be found".  These errors occur if we try to navigate between the two pages.  The reason for having more than 1 page open is that one page could be used for inquiring, while the other page is used for transacting.  The open pages may or may not be the same page (source).