It appears that the LL HLS playlist provided is missing the required EXT-X-RENDITION-REPORT. That leads to the player dropping out of low latency mode. Note that the spec requires that every LL-HLS Media Playlist contain a Rendition Report for every other Media Playlist in the MVP Should you find that a missing rendition report is not the issue, please file a bug report following steps at https://developer.apple.com/services-account/download?path=/iOS/iOS_Logs/CoreMedia_Logging_Instructions.pdf

If you're able to reproduce this issue, could you please file a but report, using the steps here: https://developer.apple.com/services-account/download?path=/iOS/iOS_Logs/CoreMedia_Logging_Instructions.pdf