There are following 2 bugs/issues present in Askbug v3.1.3 (I don’t know if these are appearing for me only, as no one else has reported it).
Fatal error: Call to undefined function ap_post_comments() in /<–my site–>/wp-content/themes/askbug/anspress/single-question.php on line 101
Fatal error: Call to undefined function is_ap_user() in /<–my site–>/wp-content/themes/askbug/templates/anspress.php on line 13
Only fix, I was able to do that to temporarily remove checking both functions from their respective places.
Kindly look into this.