a!startProcessLink() is showing different behavior at different place

I have an issue related to a!startProcessLink() function. According to my current scenario on task tab inside tempo, When user opens any task there is a link which on click opens a new interface form. After clicking OK button inside the interface form which is opened by the link, User is again navigated to the task page where exactly the link is available. This is the expected behavior but what happen is the same task form is getting opened from sites page and when user click on the link and subsequently click on OK button inside the interface form which is opened from the link, In-spite of getting to the task page they are redirected to the parent page from where they had launched the task.  

for eg: Inside Tempo

Tasks>Task1(here the link is available and after clicking>Interface form(it contains OK button),

So If user clicks on the OK button the control is again transferred to Task1 page. Now, On Site

Site>Task Queue> Task1(link)>Interface form(OK Button), 

If user clicks on OK button here then in-spite of getting redirected to Task1 they will redirected to Task Queue. I used a!startProcessLink() function to accomplish this facility. Can somebody tell me why exactly it is happening?