My initial hypothesis is that internal factors may be responsible for the 20% decline in Month-on-Month retention. For instance, Instagram might have introduced a new feature or update that hasn't resonated well with users. We would need to gather user data and feedback to confirm this. To understand the situation better, I would first examine the usage statistics from the period when the update was launched. A significant decline following the release could indicate that the update is the culprit. Additionally, I would review the app store ratings before and after the update. If there is a marked increase in negative reviews regarding the new feature or the functionality impacted by the update, that would serve as another sign of the issue. As a potential remedy, we may need to reassess the contentious feature and address the concerns raised by users in their feedback. Furthermore, advocating for a more iterative approach to releases could be beneficial. This would minimize the possible adverse effects of an update or feature, providing the team with an opportunity to resolve issues before they have a significant impact on user retention.