shortcode problem

Hi,
I use enfold on my site. I want to serve different versions of the same post to the viewers.
i created a short code to check if the device is mobile, then serves the contents of a post, else serves the content of another post.
the problem is if the content is created with avia page builfer the content shows after the <main> tag. but if its simply html everything is fine and output is in the right place.

i tried hooking to the_content, i have the same problem. if my code runs after priority 11 (do_shortcode) the cource code appears in the right place but contains the shortcodes. if i change it to normal priority (run the shortcodes and see the html output) content shows after </main> tag.

this is driving me crazy, please help

thank you