We call a simple function that waits for the page to load for any post backs that occur within our application, and I've had to add a 1 second delay to that function to deal with similar issues you are describing.
We have over 5000 test cases and from time to time I see issues with Test Execute moving too fast and not recognizing an object on the page (even with the post back function), so I periodically add in waits for those troublesome objects as they occur.
Our function that handles post backs
Sub subPageSync()
Do While Aliases.pageSchooltool.Busy
Aliases.pageSchooltool.Wait()
Loop
Delay (1000)
End Sub
