iOS showing different results from API calls than android

A client of mine is reporting a strange issue with their Ionic 3 app (recently upgraded from Ionic 1). There is an API call made to their API which returns a list of staff members. This list was recently changed. The client is reporting iOS users are seeing the old data. My first thought was this is a caching issue present on iOS.

However, they are even reporting a user who just downloaded the app is seeing the old data.

When I make the request through Postman, the data returned is correct, so I know the API isn’t improperly caching. Additionally, Android users are seeing the up to date data.

Has anyone ever experienced an issue like this? I am at a total loss as to how to troubleshoot this issue. Any help/resources would be appreciated.