I would recommend to any self respecting developers to NOT invest their precious time interviewing for Instabox. They give ANY reason to reject which makes no sense and they are not stable with any of their interview process.
I invested clearing all the three interview rounds and even cleard the pair to pair 2 hour long coding session and after three rounds and a successful pair to pair session they mentioned they are afraid about the cultural fit. The actually took cultural fit interview as a first round and came back to me saying that I was very good culturally fit and after clearing rounds they said "I answered everything and did all the code pair to pair assignment perfectly but they are not sure about the cultural fit".
They also gave some iternal "team dynamics" reason and mentioned that "Had the situation withing the team was this and that then the outcome would have been successful". Honestly their feedback didn't even made sense as I was literally regretting investing so much time during work hours to interview for them when they don't even want to hire people and the reasoning they give is crazy. Looks like coming from a toddler and not a company.
Glassdoor is never wrong and other's have posted their negative experience as well. This company will not respect your time and if you are after a job then Instabox won't provide you with one either. They can successfully make you frustated though by wasting your time.