So after a few hours of reflection and insights provided by
@MM345 I think it's not just one thing that causes VOs to question eligibility. It's a bunch of things combined. So if you are a prospective applicant I would recommend to pay close attention to your file if one or more of the following applies to you:
1) Prior to your marriage, you do not have a lot of communication proof with your spouse.
2) The sponsor left shortly after marriage and didn't have a good reason for it, like studies or job.
3) There is an age difference that is out of the norm for your society. Unfortunately we don't hear much of wives being older to their husbands so any such cases could raise concerns (in combination with other things)
4) If the marriage is a Nikkah only case. for immigration it is better to perform rukhsati.
5) If this is the PA's or Sponsors second marriage.
6) If the PA has stayed past visa limit in another country.
Now this is not to say that if this applies to you, you will for sure get called for an interview. It just means prepare your files thoroughly. Provide explanations with proof to any of those.
For instance, I stayed with my husband only ten days before coming back to Canada but I was enrolled in uni full time. I sent proof of enrollment which I got from my Uni, and explained my reasons for not staying with my husband longer on a separate sheet. I also booked my flight for after my semester ended to show intent to visit him a few months later.
All the best to all!