Banking App no good.

Since downloading the Absa Banking App, there are 2 persistent issues: 1. Whenever I try to make an online purchase (Safari browser), the server drops the connection at the payment verification stage, no matter how quickly I verify the payment. The app indicates that the payment has been verified, but it never completes the transaction. This happens no matter what Apple machine I use, across different vendors. Sometimes the transaction is successful after multiple attempts. If I pay through Apple Pay or Paypal, the transaction is always successful, first time. I have tried many times to speak to a tech, to no avail. The tech solution that one rep offered up is that Chrome is the preferred browser. Surely this cannot be the correct solution? 2. The app is slow at log in, and throughout - the spinning red wheel..based on the above tech response, I haven't queried this. It is certainly nothing to do with the phone (unless the app only works properly on an Android operating system...)