Not sure we can help answer anything on this thread without a repro, or more details. Can you perhaps provide a repro, code, github sample, or something that would demonstrate the issue that you are having so we could help further?
I dont have any experience with Ionic + AMP player. Can I suggest that you also try the solution out with the Shaka and or the HLS.js player to see if it is also exhibiting that same behavior?
iOS typically uses native AVPlayer framework for playback. In the case of the Azure Media Player, we just hand off the HLS manifest to the core AVPlayer framework in iOS and the player built into the operating system then parses that manifest and continues with the playback path. So issues identified on the Apple device are usually pointing to something going on in the Apple player engine, or something specific to the HLS content that is published. Are you able to load the HLS manifest (format=m3u8-cmaf) directly into the player on iOS and see that same behavior (just email the URL for the HLS manifest to a phone and click on it and see the playback).
Also, recommend that you test using the CMAF manifest (MP4 based and not TS) for HLS on the latest iPhones. You get that with the /manifest(format=m3u8-cmaf) option on the AMS dynamic packager when publishing your Streaming Locators.